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>

src/modes/agent/index.ts

@@ -149,6 +149,14 @@ export const agentMode: Mode = {
       claudeArgs = `--mcp-config '${escapedOurConfig}'`;
     }
 
+    // Add JSON schema if provided
+    const jsonSchemaStr = process.env.JSON_SCHEMA || "";
+    if (jsonSchemaStr) {
+      // CLI validates schema - just escape for safe shell passing
+      const escapedSchema = jsonSchemaStr.replace(/'/g, "'\\''");
+      claudeArgs += ` --json-schema '${escapedSchema}'`;
+    }
+
     // Append user's claude_args (which may have more --mcp-config flags)
     claudeArgs = `${claudeArgs} ${userClaudeArgs}`.trim();
 

src/modes/tag/index.ts

@@ -177,6 +177,14 @@ export const tagMode: Mode = {
     // Add required tools for tag mode
     claudeArgs += ` --allowedTools "${tagModeTools.join(",")}"`;
 
+    // Add JSON schema if provided
+    const jsonSchemaStr = process.env.JSON_SCHEMA || "";
+    if (jsonSchemaStr) {
+      // CLI validates schema - just escape for safe shell passing
+      const escapedSchema = jsonSchemaStr.replace(/'/g, "'\\''");
+      claudeArgs += ` --json-schema '${escapedSchema}'`;
+    }
+
     // Append user's claude_args (which may have more --mcp-config flags)
     if (userClaudeArgs) {
       claudeArgs += ` ${userClaudeArgs}`;