fix(ci): simplify test runner to plain bun test by fixing mock.module() leakage

- Add afterAll(() => { mock.restore() }) to 52 test files missing cleanup
- Rewrite create-tool-guard-hooks.test.ts to use spyOn instead of barrel mock
- Fix skill-mcp-manager OAuth tests with missing mockTokens/mockLogin definitions
- Fix start-work hook: show worktree active block on resume with existing worktree_path
- Extract createWorktreeActiveBlock to worktree-block.ts to avoid circular import
- Replace 80-line isolated test runner CI config with single `bun test` command

src/features/background-agent/session-status-classifier.test.ts

@@ -1,9 +1,11 @@
-import { describe, test, expect, mock } from "bun:test"
+import { describe, test, expect, mock, afterAll } from "bun:test"
 import { isActiveSessionStatus, isTerminalSessionStatus } from "./session-status-classifier"
 
 const mockLog = mock()
 mock.module("../../shared", () => ({ log: mockLog }))
 
+afterAll(() => { mock.restore() })
+
 describe("isActiveSessionStatus", () => {
   describe("#given a known active session status", () => {
     test('#when type is "busy" #then returns true', () => {