Convert CI workflow to Go (build + vet)

agentbbs is a Go project (go.mod, go 1.26); the Node/pnpm workflow could
never pass here — pnpm/action-setup found no packageManager. Replace with
go build + go vet. Companion test.yml runs go test.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -1,7 +1,6 @@
-# Managed by sh1pt Actions Fleet
-# pack: node-pnpm-ci@1.1.0
-# install: sh1pt-actions-store
-# hash: sha256:8e71a56cc0f13b1fdeaf4efe58c3008efcbb8b52b4194cbe9dd5b52a4c023d50
+# Go CI for agentbbs. agentbbs is a Go project (see go.mod), so this builds and
+# vets every package on pushes to main and on pull requests. The companion
+# test.yml runs `go test`.
 name: CI
 
 on:
@@ -23,18 +22,11 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      # pnpm version is read from the "packageManager" field in package.json.
-      # Do not pin a version here — it conflicts with packageManager and fails
-      # with ERR_PNPM_BAD_PM_VERSION.
-      - uses: pnpm/action-setup@v4
-
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-go@v5
         with:
-          node-version: '22'
-          cache: pnpm
+          go-version: '1.26'
+          cache: true
 
-      - run: pnpm install --frozen-lockfile
+      - run: go build ./...
 
-      - run: pnpm typecheck
-
-      - run: pnpm test
+      - run: go vet ./...