Build Pi's dist in the plugin check and read the old getter from a fixture

The auto-search review tests load Pi's worker bundle, which the plugin job
stopped building once CI scoped each package's build to its own job. One
test read a master commit through git show, which CI's shallow clone lacks;
the getter source is now a checked-in fixture.

Co-authored-by: Alfonso <alfonso-magic-context@users.noreply.github.com>

Author: ualtinok

.github/workflows/ci.yml

@@ -79,6 +79,8 @@ jobs:
         run: |
           bun run --cwd packages/plugin build
           bun run --cwd packages/cli build
+          # Plugin tests load the Pi worker bundles from packages/pi-plugin/dist.
+          bun run --cwd packages/pi-plugin build
 
       - name: Check compiled TUI freshness
         run: bun run --cwd packages/plugin check:tui-compiled