CI: save cache on each run

.github/workflows/main.yml

@@ -21,8 +21,12 @@ jobs:
       - name: Cache cache.db
         uses: actions/cache@v3
         with:
-          path: .cache
-          key: ${{ runner.os }}-v1
+          path: |
+            .cache
+          key: ${{ runner.os }}-v1-${{ github.sha }}
+          # If source files changed but packages didn't, rebuild from a prior cache.
+          restore-keys: |
+            ${{ runner.os }}-v1
       - run: bun install
       - run: bun run build
       - name: Deploy