v0.8.0

Add Grafana connector + rewrite README for current state

- New grafana connector (group Dev, observability): search dashboards, get
  dashboard, list datasources, list alerts; create annotation gated behind
  Writer; bearer token auth; --manifest + --test-connection. Wired into
  workspace, both CI bin-lists, app embed, registry (now 14), site.
- README rewritten to match reality: 14 connectors grouped correctly, the
  control-panel desktop app as the recommended install (was wrongly listed as
  roadmap), direct .mcpb path, Viewer/Writer explained, privacy note, honest
  that installers are unsigned. Zero em-dashes.
- 23 E2E green; app compiles with Grafana embedded.