fix(ci): explicitly install Cypress binary before tests

Match the npm workflow structure where dependencies are installed first,
then the cypress-io/github-action uses the already-installed Cypress.

Root cause: pnpm install --frozen-lockfile was not triggering Cypress's
postinstall script to download the binary (~100MB). The cypress/browsers
Docker image does not include the Cypress binary pre-installed.

Solution:
1. Run pnpm install --frozen-lockfile in regression-test
2. Explicitly run `pnpm exec cypress install` to force binary download
3. Use install: false in cypress-io/github-action (already installed)
4. Cache ~/.cache/Cypress using lockfile hash (from cypress-io/github-action#1138)
5. Remove CYPRESS_CACHE_FOLDER override - use image defaults

This matches the npm workflow which runs `npm ci` (triggers postinstall),
then uses the action with the pre-installed Cypress.

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

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

Author: balzss

.github/workflows/visual-regression.yml

@@ -20,11 +20,19 @@ jobs:
         with:
           node-version: '22'
           cache: 'pnpm'
+      - name: Cache Cypress binary
+        uses: actions/cache@v4
+        with:
+          path: ~/.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: Install Cypress binary
+        run: pnpm exec cypress install
+        working-directory: regression-test
       - name: Run Cypress tests
         uses: cypress-io/github-action@v6
         env: