feat: add structured output support

Add support for Agent SDK structured outputs.

New input: json_schema - JSON schema for validated outputs
Auto-sets GitHub Action outputs for each field

Security:
- Reserved output protection (prevents shadowing)
- 1MB output size limits enforced
- Output key format validation
- Objects/arrays >1MB skipped (not truncated to invalid JSON)

Tests:
- 26 unit tests
- 5 integration tests
- 480 tests passing

Docs: https://docs.claude.com/en/docs/agent-sdk/structured-outputs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.github/workflows/test-structured-output.yml

@@ -0,0 +1,327 @@
+name: Test Structured Outputs
+
+on:
+  push:
+    branches:
+      - main
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  test-basic-types:
+    name: Test Basic Type Conversions
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+
+      - name: Test with explicit values
+        id: test
+        uses: ./base-action
+        with:
+          prompt: |
+            Run this command: echo "test"
+
+            Then return EXACTLY these values:
+            - text_field: "hello"
+            - number_field: 42
+            - boolean_true: true
+            - boolean_false: false
+          json_schema: |
+            {
+              "type": "object",
+              "properties": {
+                "text_field": {"type": "string"},
+                "number_field": {"type": "number"},
+                "boolean_true": {"type": "boolean"},
+                "boolean_false": {"type": "boolean"}
+              },
+              "required": ["text_field", "number_field", "boolean_true", "boolean_false"]
+            }
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          allowed_tools: "Bash"
+
+      - name: Verify outputs
+        run: |
+          # Test string pass-through
+          if [ "${{ steps.test.outputs.text_field }}" != "hello" ]; then
+            echo "❌ String: expected 'hello', got '${{ steps.test.outputs.text_field }}'"
+            exit 1
+          fi
+
+          # Test number → string conversion
+          if [ "${{ steps.test.outputs.number_field }}" != "42" ]; then
+            echo "❌ Number: expected '42', got '${{ steps.test.outputs.number_field }}'"
+            exit 1
+          fi
+
+          # Test boolean → "true" conversion
+          if [ "${{ steps.test.outputs.boolean_true }}" != "true" ]; then
+            echo "❌ Boolean true: expected 'true', got '${{ steps.test.outputs.boolean_true }}'"
+            exit 1
+          fi
+
+          # Test boolean → "false" conversion
+          if [ "${{ steps.test.outputs.boolean_false }}" != "false" ]; then
+            echo "❌ Boolean false: expected 'false', got '${{ steps.test.outputs.boolean_false }}'"
+            exit 1
+          fi
+
+          echo "✅ All basic type conversions correct"
+
+  test-complex-types:
+    name: Test Arrays and Objects
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+
+      - name: Test complex types
+        id: test
+        uses: ./base-action
+        with:
+          prompt: |
+            Run: echo "ready"
+
+            Return EXACTLY:
+            - items: ["apple", "banana", "cherry"]
+            - config: {"key": "value", "count": 3}
+            - empty_array: []
+          json_schema: |
+            {
+              "type": "object",
+              "properties": {
+                "items": {
+                  "type": "array",
+                  "items": {"type": "string"}
+                },
+                "config": {"type": "object"},
+                "empty_array": {"type": "array"}
+              },
+              "required": ["items", "config", "empty_array"]
+            }
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          allowed_tools: "Bash"
+
+      - name: Verify JSON stringification
+        run: |
+          # Arrays should be JSON stringified
+          ITEMS='${{ steps.test.outputs.items }}'
+          if ! echo "$ITEMS" | jq -e '. | length == 3' > /dev/null; then
+            echo "❌ Array not properly stringified: $ITEMS"
+            exit 1
+          fi
+
+          # Objects should be JSON stringified
+          CONFIG='${{ steps.test.outputs.config }}'
+          if ! echo "$CONFIG" | jq -e '.key == "value"' > /dev/null; then
+            echo "❌ Object not properly stringified: $CONFIG"
+            exit 1
+          fi
+
+          # Empty arrays should work
+          EMPTY='${{ steps.test.outputs.empty_array }}'
+          if ! echo "$EMPTY" | jq -e '. | length == 0' > /dev/null; then
+            echo "❌ Empty array not properly stringified: $EMPTY"
+            exit 1
+          fi
+
+          echo "✅ All complex types JSON stringified correctly"
+
+  test-edge-cases:
+    name: Test Edge Cases
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+
+      - name: Test edge cases
+        id: test
+        uses: ./base-action
+        with:
+          prompt: |
+            Run: echo "test"
+
+            Return EXACTLY:
+            - zero: 0
+            - empty_string: ""
+            - negative: -5
+            - decimal: 3.14
+          json_schema: |
+            {
+              "type": "object",
+              "properties": {
+                "zero": {"type": "number"},
+                "empty_string": {"type": "string"},
+                "negative": {"type": "number"},
+                "decimal": {"type": "number"}
+              },
+              "required": ["zero", "empty_string", "negative", "decimal"]
+            }
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          allowed_tools: "Bash"
+
+      - name: Verify edge cases
+        run: |
+          # Zero should be "0", not empty or falsy
+          if [ "${{ steps.test.outputs.zero }}" != "0" ]; then
+            echo "❌ Zero: expected '0', got '${{ steps.test.outputs.zero }}'"
+            exit 1
+          fi
+
+          # Empty string should be empty (not "null" or missing)
+          if [ "${{ steps.test.outputs.empty_string }}" != "" ]; then
+            echo "❌ Empty string: expected '', got '${{ steps.test.outputs.empty_string }}'"
+            exit 1
+          fi
+
+          # Negative numbers should work
+          if [ "${{ steps.test.outputs.negative }}" != "-5" ]; then
+            echo "❌ Negative: expected '-5', got '${{ steps.test.outputs.negative }}'"
+            exit 1
+          fi
+
+          # Decimals should preserve precision
+          if [ "${{ steps.test.outputs.decimal }}" != "3.14" ]; then
+            echo "❌ Decimal: expected '3.14', got '${{ steps.test.outputs.decimal }}'"
+            exit 1
+          fi
+
+          echo "✅ All edge cases handled correctly"
+
+  test-name-sanitization:
+    name: Test Output Name Sanitization
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+
+      - name: Test special characters in field names
+        id: test
+        uses: ./base-action
+        with:
+          prompt: |
+            Run: echo "test"
+            Return EXACTLY: {test-result: "passed", item_count: 10}
+          json_schema: |
+            {
+              "type": "object",
+              "properties": {
+                "test-result": {"type": "string"},
+                "item_count": {"type": "number"}
+              },
+              "required": ["test-result", "item_count"]
+            }
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          allowed_tools: "Bash"
+
+      - name: Verify sanitized names work
+        run: |
+          # Hyphens should be preserved (GitHub Actions allows them)
+          if [ "${{ steps.test.outputs.test-result }}" != "passed" ]; then
+            echo "❌ Hyphenated name failed"
+            exit 1
+          fi
+
+          # Underscores should work
+          if [ "${{ steps.test.outputs.item_count }}" != "10" ]; then
+            echo "❌ Underscore name failed"
+            exit 1
+          fi
+
+          echo "✅ Name sanitization works"
+
+  test-execution-file-structure:
+    name: Test Execution File Format
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4
+
+      - name: Run with structured output
+        id: test
+        uses: ./base-action
+        with:
+          prompt: "Run: echo 'complete'. Return: {done: true}"
+          json_schema: |
+            {
+              "type": "object",
+              "properties": {
+                "done": {"type": "boolean"}
+              },
+              "required": ["done"]
+            }
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          allowed_tools: "Bash"
+
+      - name: Verify execution file contains structured_output
+        run: |
+          FILE="${{ steps.test.outputs.execution_file }}"
+
+          # Check file exists
+          if [ ! -f "$FILE" ]; then
+            echo "❌ Execution file missing"
+            exit 1
+          fi
+
+          # Check for structured_output field
+          if ! jq -e '.[] | select(.type == "result") | .structured_output' "$FILE" > /dev/null; then
+            echo "❌ No structured_output in execution file"
+            cat "$FILE"
+            exit 1
+          fi
+
+          # Verify the actual value
+          DONE=$(jq -r '.[] | select(.type == "result") | .structured_output.done' "$FILE")
+          if [ "$DONE" != "true" ]; then
+            echo "❌ Wrong value in execution file"
+            exit 1
+          fi
+
+          echo "✅ Execution file format correct"
+
+  test-summary:
+    name: Summary
+    runs-on: ubuntu-latest
+    needs:
+      - test-basic-types
+      - test-complex-types
+      - test-edge-cases
+      - test-name-sanitization
+      - test-execution-file-structure
+    if: always()
+    steps:
+      - name: Generate Summary
+        run: |
+          echo "# Structured Output Tests (Optimized)" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "Fast, deterministic tests using explicit prompts" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "| Test | Result |" >> $GITHUB_STEP_SUMMARY
+          echo "|------|--------|" >> $GITHUB_STEP_SUMMARY
+          echo "| Basic Types | ${{ needs.test-basic-types.result == 'success' && '✅ PASS' || '❌ FAIL' }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Complex Types | ${{ needs.test-complex-types.result == 'success' && '✅ PASS' || '❌ FAIL' }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Edge Cases | ${{ needs.test-edge-cases.result == 'success' && '✅ PASS' || '❌ FAIL' }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Name Sanitization | ${{ needs.test-name-sanitization.result == 'success' && '✅ PASS' || '❌ FAIL' }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| Execution File | ${{ needs.test-execution-file-structure.result == 'success' && '✅ PASS' || '❌ FAIL' }} |" >> $GITHUB_STEP_SUMMARY
+
+          # Check if all passed
+          ALL_PASSED=${{
+            needs.test-basic-types.result == 'success' &&
+            needs.test-complex-types.result == 'success' &&
+            needs.test-edge-cases.result == 'success' &&
+            needs.test-name-sanitization.result == 'success' &&
+            needs.test-execution-file-structure.result == 'success'
+          }}
+
+          if [ "$ALL_PASSED" = "true" ]; then
+            echo "" >> $GITHUB_STEP_SUMMARY
+            echo "## ✅ All Tests Passed" >> $GITHUB_STEP_SUMMARY
+          else
+            echo "" >> $GITHUB_STEP_SUMMARY
+            echo "## ❌ Some Tests Failed" >> $GITHUB_STEP_SUMMARY
+            exit 1
+          fi