fix: clear updater pubkey in build workflow to skip signing

The updater plugin has a pubkey configured which triggers signing even
with createUpdaterArtifacts disabled. Clear the pubkey via config override.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: CodeGhost21

.github/workflows/build.yml

@@ -73,6 +73,6 @@ jobs:
         run: cd skills && yarn install --frozen-lockfile
 
       - name: Build Tauri app
-        run: yarn tauri build -c '{"bundle":{"createUpdaterArtifacts":false}}' -- --target x86_64-unknown-linux-gnu
+        run: yarn tauri build -c '{"bundle":{"createUpdaterArtifacts":false},"plugins":{"updater":{"pubkey":""}}}' -- --target x86_64-unknown-linux-gnu
         env:
           NODE_ENV: production