v0.4.2

Bugfix release:
- fix: stop opencode.json wipe and install panic on failure paths (#17)
- fix: make plugin update atomic with rollback on download failure
- fix: skip submodule recursion when cloning plugin source
- fix: detect and recover from corrupted git clones in plugin cache
- docs: complete AGENTS.md navigation table

Release v0.2.0: Use manifest name for added marketplaces

fix: add test fixtures to git and set explicit commit author for CI