feat: add repository_dispatch event support (#546)

* feat: add repository_dispatch event support

Add support for repository_dispatch events in GitHub context parsing system. This enables the action to handle custom API-triggered events properly.

Changes:
- Add RepositoryDispatchEvent type definition
- Include repository_dispatch in automation event names
- Update context parsing to handle repository_dispatch events
- Update documentation to reflect repository_dispatch availability

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

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

* style: format code with prettier

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

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

* test: add comprehensive repository_dispatch event test coverage

- Add mockRepositoryDispatchContext with realistic payload structure
- Add repository_dispatch mode detection tests in registry.test.ts
- Add repository_dispatch trigger tests in agent.test.ts
- Ensure repository_dispatch events are properly handled as automation events
- Verify agent mode trigger behavior with and without prompts
- All 394 tests passing with new coverage

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

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

* style: format test files with prettier

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

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

---------

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

docs/custom-automations.md

@@ -21,7 +21,7 @@ This action supports the following GitHub events ([learn more GitHub event trigg
 - `issues` - When issues are opened or assigned
 - `pull_request_review` - When PR reviews are submitted
 - `pull_request_review_comment` - When comments are made on PR reviews
-- `repository_dispatch` - Custom events triggered via API (coming soon)
+- `repository_dispatch` - Custom events triggered via API
 - `workflow_dispatch` - Manual workflow triggers (coming soon)
 
 ## Automated Documentation Updates