Adds a Known Limitations section to docs/agent-runtime/workspace-runtime.md
explaining that the base molecule-ai-workspace-runtime image intentionally
omits Chromium system libs (libnss3, libatk-bridge2.0-0, libxkbcommon0, etc.)
to keep the shared image lean for every workspace role.
Records the recommended workflow (E2E in CI on the Gitea Actions self-hosted
runner) and points future role-specific QA/FE templates at layering
playwright install-deps on top of the base image rather than baking it in.
Closes the documentation half of molecule-ai/molecule-app#7.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
