feat: add support for omp

[rcmorano]

Add support for omp (oh-my-pi) as a host runtime

This extension currently targets pi. omp is a fork of pi with a legacy-compat layer that already remaps most of the extension's imports (@earendil-works/* → bundled host packages, bare typebox → omptype facade, StringEnum/getSettingsListTheme/SettingsList all served). A few real divergences blocked it from loading. This PR resolves them so the same package runs unmodified on both hosts.

Changes

Runtime compatibility (src/index.ts, src/gitnexus.ts)

• before_agent_start: omp passes systemPrompt as string[] (pi: string). The old string-concatenation comma-mangled omp's prompt sections ("part one,part two"). Now branches on Array.isArray and appends the GitNexus note in the host's own shape.
• SEARCH_TOOLS: added glob — omp renamed find → glob.
• extractPattern: routes glob through the existing find branch (omp's glob tool uses the path param, already covered).

Packaging (package.json)

• Added an omp manifest section mirroring pi, so omp discovers the extension entry and bundled skills from the package manifest.

Marketplace (.omp-plugin/marketplace.json)

• New catalog so the repo works as an omp marketplace source (local dir or git repo) via omp plugin marketplace add, not just the npm registry.

Docs (README.md)

• Mention omp alongside pi; add a marketplace install section (remote-git + local-dir) with the pi-gitnexus@pi-gitnexus plugin id and the bare-dot / session-restart gotchas.

Verification

• biome lint + tsc typecheck clean; 50 tests pass (2 new: pi-string and omp-string[] prompt shapes, the latter asserting no comma-mangle).
• Installed into a live omp instance via omp install . and via the marketplace (using this PR's fork, which mimicks the end result omp plugin marketplace add rcmorano/pi-gitnexus && omp plugin install pi-gitnexus@pi-gitnexus)
• RPC smoke test confirms the gitnexus command + subcommand completions register with zero extension_error frames.
  • Also tried directly installing directly from this PR's fork with `

Notes

• read_many / find branches stay dead-but-harmless on omp (pi-only), preserving dual-host support.
• The remote-git marketplace form isn't directly testable until the catalog is pushed to the upstream repo, but the GitHub-shorthand path and catalog format match omp's marketplace docs and the local-dir equivalent works.