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>

src/github/context.ts

@@ -7,9 +7,8 @@ import type {
   PullRequestReviewEvent,
   PullRequestReviewCommentEvent,
 } from "@octokit/webhooks-types";
-import type { ModeName } from "../modes/registry";
-import { DEFAULT_MODE } from "../modes/registry";
-import { isValidMode } from "../modes/registry";
+import type { ModeName } from "../modes/types";
+import { DEFAULT_MODE, isValidMode } from "../modes/registry";
 
 export type ParsedGitHubContext = {
   runId: string;