fix(ci): add explicit Cypress binary cache for Docker container

Following the solution from cypress-io/github-action#1138, explicitly
cache the Cypress binary separately from pnpm dependencies.

Changes:
- Add actions/cache@v4 step to cache /github/home/.cache/Cypress
- Cache key includes regression-test/pnpm-lock.yaml hash
- Remove explicit install steps and let cypress-io/github-action handle installation
- Remove install: false to allow action to manage Cypress installation

The action will:
1. On first run: install Cypress binary and cache it
2. On subsequent runs: restore binary from cache
3. Automatically detect and use pnpm from the workspace

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: balzss

.github/workflows/visual-regression.yml

@@ -20,17 +20,18 @@ jobs:
         with:
           node-version: '22'
           cache: 'pnpm'
+      - name: Cache Cypress binary
+        uses: actions/cache@v4
+        with:
+          path: /github/home/.cache/Cypress
+          key: ${{ runner.os }}-cypress-${{ hashFiles('regression-test/pnpm-lock.yaml') }}
       - name: Build InstUI
         run: pnpm install --frozen-lockfile && pnpm run bootstrap
-      - name: Install regression-test dependencies
-        run: pnpm install --frozen-lockfile
-        working-directory: regression-test
       - name: Run Cypress tests
         uses: cypress-io/github-action@v6
         env:
           ELECTRON_EXTRA_LAUNCH_ARGS: "--remote-debugging-port=9222"
         with:
-          install: false
           build: pnpm run build
           start: pnpm start
           working-directory: regression-test