test: add integration tests for clone/parse/pipeline, fix chunker edge case

- tests/integration-test.ts: clones p-limit repo, parses, generates diagrams (11/11 pass)
- tests/pipeline-test.ts: mock LLM provider pipeline test (29/29 pass)
- Fix chunkCode to handle single lines exceeding maxChars limit
- Add tsx devDependency for test execution

package.json

@@ -14,6 +14,8 @@
     "db:push": "turbo db:push"
   },
   "devDependencies": {
+    "simple-git": "^3.30.0",
+    "tsx": "^4.21.0",
     "turbo": "^2",
     "typescript": "^5.7"
   },