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>

test/modes/registry.test.ts

@@ -2,7 +2,11 @@ import { describe, test, expect } from "bun:test";
 import { getMode, isValidMode } from "../../src/modes/registry";
 import { agentMode } from "../../src/modes/agent";
 import { tagMode } from "../../src/modes/tag";
-import { createMockContext, createMockAutomationContext } from "../mockContext";
+import {
+  createMockContext,
+  createMockAutomationContext,
+  mockRepositoryDispatchContext,
+} from "../mockContext";
 
 describe("Mode Registry", () => {
   const mockContext = createMockContext({
@@ -50,6 +54,34 @@ describe("Mode Registry", () => {
     expect(mode.name).toBe("agent");
   });
 
+  test("getMode auto-detects agent for repository_dispatch event", () => {
+    const mode = getMode(mockRepositoryDispatchContext);
+    expect(mode).toBe(agentMode);
+    expect(mode.name).toBe("agent");
+  });
+
+  test("getMode auto-detects agent for repository_dispatch with client_payload", () => {
+    const contextWithPayload = createMockAutomationContext({
+      eventName: "repository_dispatch",
+      payload: {
+        action: "trigger-analysis",
+        client_payload: {
+          source: "external-system",
+          metadata: { priority: "high" },
+        },
+        repository: {
+          name: "test-repo",
+          owner: { login: "test-owner" },
+        },
+        sender: { login: "automation-user" },
+      },
+    });
+
+    const mode = getMode(contextWithPayload);
+    expect(mode).toBe(agentMode);
+    expect(mode.name).toBe("agent");
+  });
+
   // Removed test - legacy mode names no longer supported in v1.0
 
   test("getMode auto-detects agent mode for PR opened", () => {