docs: align CONTRIBUTING.md and CLAUDE.md with current toolchain

CONTRIBUTING.md: surface format-check + build in code guidelines
and the PR checklist so contributors run the same verifications
the project enforces locally.

CLAUDE.md: correct stale test framework reference (Mocha+Chai+Sinon
-> Jest) and update the test file glob to server/test/**/*.test.ts.

CLAUDE.md

@@ -25,7 +25,7 @@ cd server
 npm install
 npm run dev              # Start with hot-reload (nodemon + tsx) at http://localhost:52345
 npm run build            # TypeScript compile + path alias resolution
-npm run test             # Run Mocha tests with c8 coverage
+npm run test             # Run Jest tests with coverage
 npm run lint             # ESLint v9
 npm run lint-fix         # Auto-fix lint issues
 npm run format           # Prettier formatting
@@ -174,12 +174,13 @@ t('your.key')  // Never hardcode UI strings
 - Both use ESLint with strict settings
 
 ### Testing
-Server tests use Mocha + Chai + Sinon:
+Server tests use Jest (with `--experimental-vm-modules` for ESM):
 ```bash
-npm test                    # Run all tests with coverage
-npm test -- --grep "pattern"  # Run specific tests
+npm test                              # Run all tests with coverage
+npm test -- -t "pattern"              # Run tests matching name pattern
+npm test -- path/to/file.test.ts      # Run a specific file
 ```
-Test files: `server/tests/**/*.test.js`
+Test files: `server/test/**/*.test.ts`
 
 ## Database Models
 

CONTRIBUTING.md

@@ -283,7 +283,7 @@ Follow the [pull request checklist](#pull-request-checklist). Your PR should:
 
 ## Code guidelines
 
-- Use ESLint and Prettier (`npm run lint`).
+- Use ESLint and Prettier. Run `npm run lint` and `npm run format-check` in both `client` and `server`. If `format-check` reports issues, fix them with `npm run format` before committing.
 - Follow naming conventions: `camelCase` for variables, `PascalCase` for components, `UPPER_CASE` for constants.
 - No hard-coded strings — use `t('your.key')` for everything visible.
 - Use the shared theme and components. No magic numbers or hardcoded styles.
@@ -304,7 +304,7 @@ Before submitting your pull request, please confirm the following:
 - You used the shared theme for any styling — no magic numbers or inline styles.
 - The pull request addresses only one issue or topic.
 - You added screenshots or a video for any UI-related changes.
-- Your code passes linting and has no TypeScript errors.
+- Your code passes `npm run lint`, `npm run format-check`, and `npm run build` in both `client` and `server` with no errors.
 
 If one or more of these are missing, we may ask you to update your pull request before we can merge it.