Add mode support (#333)

* Add mode support

* update "as any" with proper "as unknwon as ModeName" casting

* Add documentation to README and registry.ts

* Add  tests for differen event types, integration flows, and error conditions

* Clean up some tests

* Minor test fix

* Minor formatting test + switch from interface to type

* correct the order of mkdir call

* always configureGitAuth as there's already a fallback to handle null users by using the bot ID

* simplify registry setup

---------

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

test/modes/registry.test.ts

@@ -0,0 +1,28 @@
+import { describe, test, expect } from "bun:test";
+import { getMode, isValidMode, type ModeName } from "../../src/modes/registry";
+import { tagMode } from "../../src/modes/tag";
+
+describe("Mode Registry", () => {
+  test("getMode returns tag mode by default", () => {
+    const mode = getMode("tag");
+    expect(mode).toBe(tagMode);
+    expect(mode.name).toBe("tag");
+  });
+
+  test("getMode throws error for invalid mode", () => {
+    const invalidMode = "invalid" as unknown as ModeName;
+    expect(() => getMode(invalidMode)).toThrow(
+      "Invalid mode 'invalid'. Valid modes are: 'tag'. Please check your workflow configuration.",
+    );
+  });
+
+  test("isValidMode returns true for tag mode", () => {
+    expect(isValidMode("tag")).toBe(true);
+  });
+
+  test("isValidMode returns false for invalid mode", () => {
+    expect(isValidMode("invalid")).toBe(false);
+    expect(isValidMode("review")).toBe(false);
+    expect(isValidMode("freeform")).toBe(false);
+  });
+});