Bundled plugin marketplace — coda-essentials

Summary

Introduces a plugin system for CODA and ships coda-essentials as the first bundled plugin. Migrating from datasciencemonkey PR #140.

Plugin loader changes (setup_claude.py):

• Stage plugins into ~/.claude/plugins/cache/ and write the state files Claude Code's plugin loader expects.
• Inject fork-wide directives (uv version floor, library floors, UC catalog name) into ~/.claude/CLAUDE.md.
• Editor detection (micro, nano, vim) for Bash deny-rule population so the user's preferred editor isn't blocked.

coda-essentials provides:

• Agents: build-feature, implementer, prd-writer, test-generator.
• Commands: /cache-stats (token cache hit rate), /til (capture learning).
• Hooks: session-context-loader, session-crystallize-nudge, push-brain-to-workspace (syncs ~/.claude/ to Databricks Workspace on commit), check-memory-staleness, mlflow-trace-stop.

claude_brain_sync.py — post-commit hook that syncs Claude brain files to Databricks Workspace for cross-session persistence.

Branch

feat/coda-essentials-plugin — about to be pushed.

Diff scope

+1220 / -31, 16 files. No tests yet — plugin marketplace flow needs an integration test before merge.

Start with setup_claude.py and claude_brain_sync.py, then review the plugin agents, commands, and hooks listed in the issue. The proposed branch and 16-file diff are already described, but no integration test exists; done means the marketplace flow is covered by an integration test and the bundled plugin sync behavior works as specified.