fix: enforce headless mode for browser automation + update README for wizard

- STANDARDS.md: add non-negotiable rule that Playwright/Cypress/Puppeteer
  must always run headless to prevent display collision with the user
- QA-TESTING.md: add Browser Automation section with per-tool headless
  configuration guidance
- README.md: update to reflect the TypeScript wizard (mosaic init modes,
  --non-interactive flags, wizard development section, dist/ in tree)

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

guides/QA-TESTING.md

@@ -79,6 +79,17 @@ Template:
 | AC-2: ... | ... | ... |
 ```
 
+## Browser Automation (Hard Rule)
+
+All browser automation (Playwright, Cypress, Puppeteer) MUST run in **headless mode**.
+Launching a visible browser collides with the user's display and active session.
+
+- Playwright: use `headless: true` in config or `--headed` must NOT be passed
+- Cypress: use `cypress run` (headless by default), never `cypress open`
+- Puppeteer: use `headless: true` (default)
+
+If a project's `playwright.config.ts` does not explicitly set `headless: true`, add it before running tests.
+
 ## Test Quality Rules
 
 1. Test behavior and outcomes, not private implementation details.