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/modes/types.ts

@@ -1,5 +1,6 @@
 import type { ParsedGitHubContext } from "../github/context";
-import type { ModeName } from "./registry";
+
+export type ModeName = "tag" | "agent";
 
 export type ModeContext = {
   mode: ModeName;
@@ -20,9 +21,9 @@ export type ModeData = {
  * Each mode defines its own behavior for trigger detection, prompt generation,
  * and tracking comment creation.
  *
- * Future modes might include:
- * - 'review': Optimized for code reviews without tracking comments
- * - 'freeform': For automation with no trigger checking
+ * Current modes include:
+ * - 'tag': Traditional implementation triggered by mentions/assignments
+ * - 'agent': For automation with no trigger checking
  */
 export type Mode = {
   name: ModeName;
@@ -39,13 +40,12 @@ export type Mode = {
   prepareContext(context: ParsedGitHubContext, data?: ModeData): ModeContext;
 
   /**
-   * Returns additional tools that should be allowed for this mode
-   * (base GitHub tools are always included)
+   * Returns the list of tools that should be allowed for this mode
    */
   getAllowedTools(): string[];
 
   /**
-   * Returns tools that should be disallowed for this mode
+   * Returns the list of tools that should be disallowed for this mode
    */
   getDisallowedTools(): string[];