fix(lint): resolve pre-existing lint errors and merge conflicts

- Remove unused imports/vars from routes.ts (VALID_TRANSITIONS, AUTOMATION_PRESETS, ChatStore, FileListResponse, etc.)
- Prefix unused destructured error vars with _ convention
- Fix prefer-const for summary variable
- Add _ ignore pattern to eslint.config.mjs
- Include test files in tsconfig.app.json to fix @testing-library/jest-dom types
- Resolve GitManagerModal.test.tsx merge conflict (take fn-1626 expectLatestCallStartsWith style)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/dashboard/tsconfig.app.json

@@ -8,6 +8,5 @@
     "noEmit": true,
     "types": ["vitest/globals", "@testing-library/jest-dom", "node", "vite/client"]
   },
-  "include": ["app/**/*"],
-  "exclude": ["app/**/*.test.ts", "app/**/*.test.tsx"]
+  "include": ["app/**/*"]
 }