The OpenCode plugin (`plugins/opencode`) is the routing shim that
carries `headroom wrap opencode` traffic through the proxy — but **no CI
job ever compiled it**. It has `typecheck`/`build`/`test` scripts that
only ran locally, so:
- TypeScript 6.x (#1687) and @types/node 26 (#1688) major-bump PRs had
**zero build evidence** (why they're held).
- Any source edit to the plugin could silently break the build.
This adds a path-gated workflow that runs `npm ci → typecheck → build →
test` whenever `plugins/opencode/**` (or this workflow) changes. Matches
repo conventions (`setup-node@v6`, node 20, npm cache).
**Verified green locally on main:** `tsc --noEmit` clean, `tsup` build
ok, 13 vitest tests pass.
Unblocks safe evaluation of the held dependency-bump PRs and protects
the routing plugin going forward.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
