feat: Add comprehensive testing infrastructure

Implements robust testing setup with Playwright global auth, reusable test
helpers, Docker support, and CI/CD integration with Gitea Actions.

## Changes

### Playwright Setup
- Add global auth setup with storage state reuse (tests/playwright/auth.setup.ts)
- Fix auth setup to clear existing state before fresh login
- Create reusable performOAuthLogin helper (tests/playwright/helpers.ts)
- Configure dotenv loading for environment variables in playwright.config.ts

### Magnitude Configuration
- Update to use Claude Sonnet 4.5 (claude-sonnet-4-5-20250514)
- Create reusable loginFlow helper (tests/magnitude/helpers.ts)
- Fix smoke test to check login page instead of non-existent homepage

### Docker Support
- Add Dockerfile.playwright with non-root user (pwuser) for security
- Uses official Playwright Docker image (mcr.microsoft.com/playwright:v1.49.1-noble)
- Provides consistent testing environment across users and CI/CD

### CI/CD Integration
- Add Gitea Actions workflow (.gitea/workflows/magnitude.yml)
- Runs Magnitude tests on every push and PR
- Starts SurrealDB and Next.js dev server automatically
- Uploads test results as artifacts (30-day retention)

### Documentation
- Add comprehensive testing setup docs to AGENTS.md:
  - Playwright Docker setup instructions
  - CI/CD with Gitea Actions
  - Testing framework separation (Playwright vs Magnitude)
  - Required secrets for CI/CD

### Testing Best Practices
- Separate Playwright (manual + global auth) from Magnitude (automated E2E)
- Reusable helpers reduce code duplication
- Both frameworks work independently

## Testing

- ✅ Playwright auth setup test passes (5.6s)
- ✅ Magnitude smoke test passes
- ✅ OAuth flow works correctly with helper function

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

AGENTS.md

@@ -102,9 +102,12 @@ These credentials should be used for all automated testing (Magnitude, Playwrigh
    - ✅ All manual testing with Playwright MCP completed and verified
    - ✅ All Magnitude tests written and cover all verified functionality
    - ✅ Database verified for expected state after operations (e.g., deletions actually removed records)
+   - ✅ Run magnitude tests for current feature FIRST: `pnpm test tests/magnitude/your-feature.mag.ts`
+   - ✅ Verify current feature tests pass
    - ✅ Run ALL magnitude tests: `pnpm test`
-   - ✅ All tests passing
+   - ✅ Verify ENTIRE test suite passes
    - ✅ No console errors or warnings in production code paths
+   - **CRITICAL**: Do NOT commit until ALL tests pass - feature tests AND full test suite
    - Only commit after ALL checklist items are complete
 
 7. **Documentation**:
@@ -114,9 +117,76 @@ These credentials should be used for all automated testing (Magnitude, Playwrigh
 **Testing Resources**:
 - Playwright Global Setup/Teardown: https://playwright.dev/docs/test-global-setup-teardown
 - Playwright Test Agents: https://playwright.dev/docs/test-agents
+- Playwright Docker: https://playwright.dev/docs/docker
 - Magnitude.run Documentation: https://magnitude.run/docs
 - Project Test README: `tests/README.md`
 
+**Playwright Docker Setup**:
+
+For consistent testing environments across users and CI/CD, use the Playwright Docker image:
+
+1. **Build the Playwright Docker image**:
+   ```bash
+   docker build -f Dockerfile.playwright -t ponderants-playwright .
+   ```
+
+2. **Run Playwright tests in Docker**:
+   ```bash
+   docker run --rm \
+     --network=host \
+     -v $(pwd):/home/pwuser/app \
+     -e TEST_BLUESKY_HANDLE \
+     -e TEST_BLUESKY_PASSWORD \
+     ponderants-playwright
+   ```
+
+3. **Benefits**:
+   - Non-root user execution (pwuser) for security
+   - Consistent browser versions across environments
+   - Isolated test environment
+   - Ready for CI/CD integration
+
+**CI/CD with Gitea Actions**:
+
+Magnitude tests run automatically on every push and pull request via Gitea Actions:
+
+1. **Configuration**: `.gitea/workflows/magnitude.yml`
+
+2. **Workflow steps**:
+   - Checkout code
+   - Setup Node.js and pnpm
+   - Start SurrealDB in Docker
+   - Start Next.js dev server with environment variables
+   - Run Magnitude tests
+   - Upload test results as artifacts
+
+3. **Required Secrets** (configure in Gitea repository settings):
+   - `ANTHROPIC_API_KEY` - For Magnitude AI vision testing
+   - `TEST_BLUESKY_HANDLE` - Test account handle
+   - `TEST_BLUESKY_PASSWORD` - Test account password
+   - `SURREALDB_USER`, `SURREALDB_PASS`, `SURREALDB_NS`, `SURREALDB_DB`
+   - `ATPROTO_CLIENT_ID`, `ATPROTO_REDIRECT_URI`
+   - `GOOGLE_API_KEY`, `DEEPGRAM_API_KEY`
+   - `SURREAL_JWT_SECRET`
+
+4. **Test results**: Available as workflow artifacts for 30 days
+
+**Testing Framework Separation**:
+
+- **Playwright**: Used for manual testing with Playwright MCP and global auth setup
+  - Location: `tests/playwright/`
+  - Helpers: `tests/playwright/helpers.ts`
+  - Auth setup: `tests/playwright/auth.setup.ts`
+  - Run: `npx playwright test`
+
+- **Magnitude**: Used for automated end-to-end testing in development and CI/CD
+  - Location: `tests/magnitude/`
+  - Helpers: `tests/magnitude/helpers.ts`
+  - Configuration: `magnitude.config.ts` (uses Claude Sonnet 4.5)
+  - Run: `npx magnitude` or `pnpm test`
+
+Both frameworks are independent and can be used separately or together depending on the testing need.
+
 You are an expert-level, full-stack AI coding agent. Your task is to implement
 the "Ponderants" application. Product Vision: Ponderants is an AI-powered
 thought partner that interviews a user to capture, structure, and visualize