v0.5.0

Add GitHub Enterprise connector + visual review fixes

- New github connector (group Dev): search repos, list/get issues, list PRs;
  create issue + comment gated behind Writer; sets GitHub Accept + User-Agent
  headers; --manifest + --test-connection. Wired into workspace, both CI
  bin-lists, app embed, registry (now 11), site descriptions. Compiles.
- Visual review (high-end): quiet glass download buttons (coral on card hover)
  to kill the "wall of orange", neutral group pills + styled count (coral now
  appears once per card), larger search field with a soft focus glow. 20 E2E green.