ci: add CI job for VS Code extension (#444)

* ci: add CI job for VS Code extension

Add .github/workflows/vscode-ext.yml to validate the VS Code extension
(extensions/vscode/) on every push/PR that touches that directory.

The workflow runs on the self-hosted node:24 container (matching the
existing CI conventions) and executes:
  - yarn install --frozen-lockfile  (lockfile integrity)
  - yarn lint                        (ESLint)
  - yarn compile                     (TypeScript + webpack dev build)
  - yarn test                        (Jest, all 10 test suites)

Path filter (extensions/vscode/**) ensures Go-only changes do not
trigger this job. No vsce package step — packaging is a release concern.

Fixes the gap identified in #441: dependency PRs from dependabot (#437)
will now receive real build and test signal before merging.

Closes #441

* ci: pin node image version and add yarn dependency caching

- Pin node container image to node:24.0.0 for reproducible builds
- Add actions/setup-node@v4 with yarn cache for extensions/vscode/yarn.lock
  to speed up CI workflow runs

* ci: use node:24 image container tag

* ci: pin node version to 24.4.1

* ci: use actions/cache@v4 for yarn package caching

* ci: remove redundant push trigger on main

Author: AyushPandey003

.github/workflows/vscode-ext.yml

@@ -0,0 +1,50 @@
+name: VS Code Extension
+
+on:
+  pull_request:
+    branches: [main]
+    paths:
+      - 'extensions/vscode/**'
+
+permissions:
+  contents: read
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  check:
+    runs-on: self-hosted
+    timeout-minutes: 10
+    container:
+      image: node:24.4.1
+    defaults:
+      run:
+        working-directory: extensions/vscode
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Trust workspace
+        run: git config --global --replace-all safe.directory '*'
+        working-directory: .
+
+      - name: Cache Yarn packages
+        uses: actions/cache@v4
+        with:
+          path: ~/.cache/yarn
+          key: ${{ runner.os }}-yarn-${{ hashFiles('extensions/vscode/yarn.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-yarn-
+
+      - name: Install dependencies
+        run: yarn install --frozen-lockfile
+
+      - name: Lint
+        run: yarn lint
+
+      - name: Compile
+        run: yarn compile
+
+      - name: Test
+        run: yarn test