refactor: improve .cache directory caching strategy

Changes:
- Move cache restore to setup-frontend action BEFORE build operations
- Remove duplicate cache step from setup-playwright action
- Use cache/restore instead of cache to avoid auto-save behavior
- Rename cache key from 'playwright-setup-cache' to 'tool-cache' for clarity
- Include source file hashes in cache key for proper invalidation

Benefits:
- Cache is now restored before tools run, allowing them to use cached data
- Eliminates duplicate caching of ./.cache directory
- Cache properly invalidates when source files or configs change
- Follows GitHub Actions best practice of restore before, save after pattern
- The workspace cache in tests-ci.yaml handles saving the complete state

Note: The .cache directory contains outputs from ESLint, Prettier, Stylelint,
Knip, and TypeScript incremental builds. These should be restored before any
build/lint operations run.

.github/actions/setup-frontend/action.yml

@@ -23,6 +23,18 @@ runs:
         cache: 'pnpm'
         cache-dependency-path: './pnpm-lock.yaml'
 
+    # Restore tool caches before running any build/lint operations
+    - name: Restore tool output cache
+      uses: actions/cache/restore@v4
+      with:
+        path: |
+          ./.cache
+          ./tsconfig.tsbuildinfo
+        key: tool-cache-${{ runner.os }}-${{ hashFiles('./pnpm-lock.yaml') }}-${{ hashFiles('./src/**/*.{ts,vue,js,mts}', './*.config.*') }}
+        restore-keys: |
+          tool-cache-${{ runner.os }}-${{ hashFiles('./pnpm-lock.yaml') }}-
+          tool-cache-${{ runner.os }}-
+
     - name: Install dependencies
       shell: bash
       run: pnpm install --frozen-lockfile

.github/actions/setup-playwright/action.yml

@@ -26,15 +26,3 @@ runs:
       if: steps.cache-playwright-browsers.outputs.cache-hit == 'true'
       shell: bash
       run: pnpm exec playwright install-deps
-
-    - name: Cache tool outputs
-      uses: actions/cache@v4
-      with:
-        path: |
-          ./.cache
-          ./tsconfig.tsbuildinfo
-        key: playwright-setup-cache-${{ runner.os }}-${{ hashFiles('./pnpm-lock.yaml') }}-${{ hashFiles('./src/**/*.{ts,vue,js}', './*.config.*') }}
-        restore-keys: |
-          playwright-setup-cache-${{ runner.os }}-${{ hashFiles('./pnpm-lock.yaml') }}-
-          playwright-setup-cache-${{ runner.os }}-
-          playwright-tools-cache-${{ runner.os }}-