feat: add agent mode for automation scenarios (#337)

* feat: add agent mode for automation scenarios

- Add agent mode that always triggers without checking for mentions
- Implement Mode interface with support for mode-specific tool configuration
- Add getAllowedTools() and getDisallowedTools() methods to Mode interface
- Simplify tests by combining related test cases
- Update documentation and examples to include agent mode
- Fix TypeScript imports to prevent circular dependencies

Agent mode is designed for automation and workflow_dispatch scenarios
where Claude should always run without requiring trigger phrases.

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

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

* Minor update to readme (from @main to @beta)

* Since workflow_dispatch isn't in the base action, update the examples accordingly

* minor formatting issue

* Update to say beta instead of main

* Fix missed tracking comment to be false

---------

Co-authored-by: km-anthropic <km-anthropic@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>

examples/claude-modes.yml

@@ -0,0 +1,56 @@
+name: Claude Mode Examples
+
+on:
+  # Common events for both modes
+  issue_comment:
+    types: [created]
+  issues:
+    types: [opened, labeled]
+  pull_request:
+    types: [opened]
+
+jobs:
+  # Tag Mode (Default) - Traditional implementation
+  tag-mode-example:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+      issues: write
+      id-token: write
+    steps:
+      - uses: anthropics/claude-code-action@beta
+        with:
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          # Tag mode (default) behavior:
+          # - Scans for @claude mentions in comments, issues, and PRs
+          # - Only acts when trigger phrase is found
+          # - Creates tracking comments with progress checkboxes
+          # - Perfect for: Interactive Q&A, on-demand code changes
+
+  # Agent Mode - Automation without triggers
+  agent-mode-auto-review:
+    # Automatically review every new PR
+    if: github.event_name == 'pull_request' && github.event.action == 'opened'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+      issues: write
+      id-token: write
+    steps:
+      - uses: anthropics/claude-code-action@beta
+        with:
+          mode: agent
+          anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+          override_prompt: |
+            Review this PR for code quality. Focus on:
+            - Potential bugs or logic errors
+            - Security concerns
+            - Performance issues
+
+            Provide specific, actionable feedback.
+          # Agent mode behavior:
+          # - NO @claude mention needed - runs immediately
+          # - Enables true automation (impossible with tag mode)
+          # - Perfect for: CI/CD integration, automatic reviews, label-based workflows