fix(ci): make WASM optional in SEA builds with graceful fallback

Apply progressive enhancement pattern to build-sea workflow to match
runtime graceful fallback behavior. The CLI runtime already handles
missing WASM gracefully via onnx-runtime-stub.mts and falls back to
baseline features (compromise library). The build workflow should do
the same instead of hard-failing.

Changes:
- Convert Windows WASM cache check from error to warning
- Skip WASM compilation on Windows (use baseline features only)
- Make Python/Emscripten setup non-Windows only
- Convert WASM verification from hard-fail to warning
- Document progressive enhancement tiers in build output

Progressive enhancement tiers:
  Tier 1 (Baseline): Pure JS with compromise - always available
  Tier 2 (Enhanced): MiniLM + ONNX Runtime - requires WASM
  Tier 3 (Full): CodeT5 - requires WASM + models

Benefits:
- Windows builds no longer blocked by missing WASM cache
- Faster builds when WASM not needed
- Consistent with runtime fallback behavior
- CLI works on all platforms with baseline features

Author: jdalton

.github/workflows/build-sea.yml

@@ -318,21 +318,27 @@ jobs:
       #             echo "✗ ONNX Runtime cache invalid or missing"
       #           fi
 
-      - name: Check WASM cache requirements (Windows)
+      - name: Check WASM cache status (Windows)
         if: steps.check-platform.outputs.should-run == 'true' && matrix.os == 'windows' && steps.yoga-cache-valid.outputs.valid != 'true'
         run: |
-          echo "::error::WASM assets not cached for Windows build. Run build-wasm.yml workflow first to prime the cache."
-          echo "Windows builds require pre-cached WASM assets due to network reliability issues."
-          exit 1
+          echo "::warning::WASM assets not cached. Build will use baseline features only."
+          echo "For enhanced NLP features, run build-wasm.yml workflow first to prime the cache."
+          echo ""
+          echo "Progressive enhancement tiers:"
+          echo "  ✓ Tier 1 (Baseline): Pure JS with compromise - always available"
+          echo "  ✗ Tier 2 (Enhanced): MiniLM + ONNX Runtime - requires WASM"
+          echo "  ✗ Tier 3 (Full): CodeT5 - requires WASM + models"
+          echo ""
+          echo "The CLI will work normally with baseline features."
 
-      - name: Setup Python for WASM builds
-        if: steps.check-platform.outputs.should-run == 'true' && steps.yoga-cache-valid.outputs.valid != 'true'
+      - name: Setup Python for WASM builds (non-Windows)
+        if: steps.check-platform.outputs.should-run == 'true' && steps.yoga-cache-valid.outputs.valid != 'true' && matrix.os != 'windows'
         uses: actions/setup-python@0b93645e9fea7318ecaed2b359559ac225c90a2b # v5.3.0
         with:
           python-version: '3.11'
 
-      - name: Cache Emscripten SDK
-        if: steps.check-platform.outputs.should-run == 'true' && steps.yoga-cache-valid.outputs.valid != 'true'
+      - name: Cache Emscripten SDK (non-Windows)
+        if: steps.check-platform.outputs.should-run == 'true' && steps.yoga-cache-valid.outputs.valid != 'true' && matrix.os != 'windows'
         id: emsdk-cache
         uses: actions/cache@0057852bfaa89a56745cba8c7296529d2fc39830 # v4.3.0
         with:
@@ -350,17 +356,17 @@ jobs:
       #       pip-${{ runner.os }}-py3.11-
       #       pip-${{ runner.os }}-
 
-      - name: Build WASM assets on cache miss
-        if: steps.check-platform.outputs.should-run == 'true' && steps.yoga-cache-valid.outputs.valid != 'true'
+      - name: Build WASM assets on cache miss (non-Windows)
+        if: steps.check-platform.outputs.should-run == 'true' && steps.yoga-cache-valid.outputs.valid != 'true' && matrix.os != 'windows'
         shell: bash
         run: |
           echo "⚠️  WASM cache miss detected - building from source"
           echo "This will take 30-60 minutes. Consider running build-wasm.yml workflow to prime cache."
           echo ""
           echo "Cache status:"
           echo "  Yoga Layout: ${{ steps.yoga-cache-valid.outputs.valid == 'true' && '✓ cached' || '✗ missing' }}"
-          #           echo "  AI Models: ${{ steps.ai-cache-valid.outputs.valid == 'true' && '✓ cached' || '✗ missing' }}"
-          #           echo "  ONNX Runtime: ${{ steps.onnx-cache-valid.outputs.valid == 'true' && '✓ cached' || '✗ missing' }}"
+          echo ""
+          echo "Note: Windows builds skip WASM compilation and use baseline features only."
           echo ""
 
           # Install Emscripten if needed for Yoga.
@@ -469,11 +475,17 @@ jobs:
           #           ls -lh packages/onnxruntime/dist/ 2>/dev/null || echo "  ❌ Directory not found"
           echo ""
 
-          # Fail fast if critical Yoga Layout WASM is missing
+          # Check if Yoga Layout WASM is available (optional with graceful fallback)
           if [ ! -f "packages/yoga-layout/build/wasm/yoga.wasm" ]; then
-            echo "::error::Yoga Layout WASM not found! Run build-wasm.yml workflow to prime cache."
-            echo "Cache status was: yoga=${{ steps.yoga-cache-valid.outputs.valid }}"
-            exit 1
+            echo "::warning::Yoga Layout WASM not found. Build will proceed with baseline features."
+            echo "For enhanced NLP features, run build-wasm.yml workflow to prime cache."
+            echo ""
+            echo "Progressive enhancement:"
+            echo "  ✓ Tier 1 (Baseline): Pure JS - CLI will work normally"
+            echo "  ✗ Tier 2 (Enhanced): MiniLM + ONNX Runtime - requires WASM"
+            echo "  ✗ Tier 3 (Full): CodeT5 - requires WASM + models"
+          else
+            echo "✓ Yoga Layout WASM available - enhanced features enabled"
           fi
 
       - name: Build CLI (required for SEA)