feat(ci): unify caching strategy across all build workflows

Implement consistent caching strategy across smol, SEA, and WASM builds:

**Unified Strategy:**
- Native C++ (smol): ccache + build directory cache
- WASM C++ (Yoga, ONNX): build directory cache only
- Non-C++ (AI, SEA): output cache only

**Changes:**

Smol build:
- Move cache key generation before ccache setup (needs hash first)
- Add build directory cache for CMake state and Node.js source
- Update ccache key to include content hash
- Preserves: ccache (object files) + build state (CMake)

Yoga build:
- Rename "Restore yoga build cache" → "Restore yoga output cache"
- Add build directory cache for CMake state and Yoga source
- Consistent with ONNX pattern

ONNX build:
- Already implemented (reference pattern)

**Benefits:**
- Consistent pattern across all C++ builds
- Better failure recovery (preserve intermediate state)
- Smol: Faster incremental builds with CMake cache
- Yoga: Faster rebuilds (though already fast at 2-3 min)
- ONNX: Already benefits from build cache (saves 30+ min on failures)

**Cache Layers:**
1. Build tools (Python, Ninja, Emscripten)
2. Source code (.node-source/, .yoga-source/, .onnx-source/)
3. Intermediate build (CMake cache, compiled objects)
4. Compilation cache (ccache, native only)
5. Final output (dist/ artifacts)

Author: jdalton

.github/workflows/build-smol.yml

@@ -81,20 +81,31 @@ jobs:
       - name: Install dependencies
         run: pnpm install --frozen-lockfile
 
-      - name: Setup ccache (Linux/macOS)
-        if: matrix.os != 'windows'
-        uses: hendrikmuhs/ccache-action@ed74d11c0b343532753ecead8a951bb09bb34bc9 # v1.2.14
-        with:
-          key: build-${{ matrix.platform }}-${{ matrix.arch }}
-          max-size: 2G
-
       - name: Generate smol build cache key
         id: smol-cache-key
         shell: bash
         run: |
           HASH=$(find patches packages/node-smol-builder/patches packages/node-smol-builder/additions scripts -type f \( -name "*.patch" -o -name "*.mjs" -o -name "*.h" -o -name "*.c" -o -name "*.cc" \) | sort | xargs sha256sum | sha256sum | cut -d' ' -f1)
           echo "hash=$HASH" >> $GITHUB_OUTPUT
 
+      - name: Setup ccache (Linux/macOS)
+        if: matrix.os != 'windows'
+        uses: hendrikmuhs/ccache-action@ed74d11c0b343532753ecead8a951bb09bb34bc9 # v1.2.14
+        with:
+          key: build-${{ matrix.platform }}-${{ matrix.arch }}-${{ steps.smol-cache-key.outputs.hash }}
+          max-size: 2G
+
+      - name: Restore smol build cache
+        id: smol-build-cache
+        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+        with:
+          path: |
+            packages/node-smol-builder/build
+            packages/node-smol-builder/.node-source
+          key: node-smol-build-${{ matrix.platform }}-${{ matrix.arch }}-${{ steps.smol-cache-key.outputs.hash }}
+          restore-keys: |
+            node-smol-build-${{ matrix.platform }}-${{ matrix.arch }}-
+
       - name: Restore smol binary cache
         id: smol-cache
         uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0

.github/workflows/build-wasm.yml

@@ -54,14 +54,25 @@ jobs:
           HASH=$(find packages/yoga-layout -type f \( -name "*.cpp" -o -name "*.h" -o -name "*.mjs" -o -name "CMakeLists.txt" \) | sort | xargs sha256sum | sha256sum | cut -d' ' -f1)
           echo "hash=$HASH" >> $GITHUB_OUTPUT
 
-      - name: Restore yoga build cache
+      - name: Restore yoga output cache
         id: yoga-cache
         uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
         with:
           path: packages/yoga-layout/build/wasm
           key: yoga-wasm-${{ steps.yoga-cache-key.outputs.hash }}
           restore-keys: yoga-wasm-
 
+      - name: Restore yoga build cache
+        id: yoga-build-cache
+        uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
+        with:
+          path: |
+            packages/yoga-layout/build
+            packages/yoga-layout/.yoga-source
+          key: yoga-build-${{ steps.yoga-cache-key.outputs.hash }}
+          restore-keys: |
+            yoga-build-
+
       - name: Verify cached artifacts
         id: yoga-cache-valid
         run: |