feat: add tests, file locking, and CI test integration

- Add vitest test framework with 24 tests across 4 test files
  - Token estimation tests (5 tests)
  - Tool executor tests (8 tests) - reads, writes, patches, deletes, shell, security, path traversal
  - Settings manager tests (4 tests) - defaults, save/load, dot paths, corrupt settings
  - Provider tests (7 tests) - model routing, retry logic with backoff
- Add file locking system (src/core/lock.ts) for concurrent agent operations
- Wire file locking into tool executor for write operations
- Add test script to package.json (npm test, npm run test:watch)
- Add npm test step to CI workflow
- Fast retry delays in test mode (10/20/30ms vs 1s/3s/8s)

Author: thegreatalxx

.github/workflows/ci.yml

@@ -32,6 +32,9 @@ jobs:
       - name: Build
         run: npm run build
 
+      - name: Run tests
+        run: npm test
+
       - name: Verify dist output
         run: |
           FILE_COUNT=$(find dist -name "*.js" | wc -l)

dist/providers/client.d.ts

@@ -1,4 +1,5 @@
 import { Provider, Message, ToolCall, ModelRouting } from '../core/types.js';
+export declare function retryWithBackoff<T>(fn: () => Promise<T>, context: string, signal?: AbortSignal): Promise<T>;
 export interface StreamChunk {
     type: 'text' | 'tool_call' | 'tool_result' | 'agent_step' | 'done' | 'error';
     text?: string;