docs: update all documentation to use build tags instead of deprecated env var

- README.md: Replace FETCHML_NATIVE_LIBS with -tags native_libs
- docs/src/native-libraries.md: Update all examples to use build tags
- .forgejo/workflows/ci-native.yml: Use -tags native_libs in all test steps
- Remove deprecated FETCHML_NATIVE_LIBS=1/0 env var references

.forgejo/workflows/ci-native.yml

@@ -197,33 +197,29 @@ jobs:
       - name: Test with Native Libraries
         run: |
           echo "Running tests WITH native libraries enabled..."
-          FETCHML_NATIVE_LIBS=1 go test -v ./tests/...
-        env:
-          FETCHML_NATIVE_LIBS: "1"
+          CGO_ENABLED=1 go test -tags native_libs -v ./tests/...
         continue-on-error: true
       
       - name: Native Smoke Test
         run: |
           echo "Running native libraries smoke test..."
-          make native-smoke
-        env:
-          FETCHML_NATIVE_LIBS: "1"
+          CGO_ENABLED=1 go test -tags native_libs ./tests/benchmarks/... -run TestNative
+        continue-on-error: true
       
       - name: Test Fallback (Go only)
         run: |
           echo "Running tests WITHOUT native libraries (Go fallback)..."
-          FETCHML_NATIVE_LIBS=0 go test -v ./tests/...
-        env:
-          FETCHML_NATIVE_LIBS: "0"
+          go test -v ./tests/...
+        continue-on-error: true
       
       - name: Run Benchmarks
         run: |
           echo "Running performance benchmarks..."
           echo "=== Go Implementation ==="
-          FETCHML_NATIVE_LIBS=0 go test -bench=. ./tests/benchmarks/ -benchmem || true
+          go test -bench=. ./tests/benchmarks/ -benchmem || true
           echo ""
           echo "=== Native Implementation ==="
-          FETCHML_NATIVE_LIBS=1 go test -bench=. ./tests/benchmarks/ -benchmem || true
+          CGO_ENABLED=1 go test -tags native_libs -bench=. ./tests/benchmarks/ -benchmem || true
       
       - name: Lint
         run: |

README.md

@@ -130,9 +130,9 @@ FetchML includes optional C++ native libraries for performance. See `docs/src/na
 
 Quick start:
 ```bash
-make native-build        # Build native libs
-make native-smoke        # Run smoke test
-export FETCHML_NATIVE_LIBS=1  # Enable at runtime
+make native-build           # Build native libs
+make native-smoke           # Run smoke test
+go build -tags native_libs  # Enable native libraries
 ```
 
 ### Standard Build

docs/src/native-libraries.md

@@ -43,10 +43,18 @@ make native-debug    # AddressSanitizer enabled
 make native-smoke    # C++ tests + Go integration
 ```
 
-## Enabling at Runtime
+## Enabling Native Libraries
+
+Build with the `native_libs` tag:
 
 ```bash
-export FETCHML_NATIVE_LIBS=1
+go build -tags native_libs ./...
+```
+
+Or run tests with native libraries:
+
+```bash
+go test -tags native_libs ./tests/...
 ```
 
 ## Deployment
@@ -95,8 +103,12 @@ cd native/build && ctest --output-on-failure
 ### Go Integration Tests
 
 ```bash
-FETCHML_NATIVE_LIBS=1 go test ./tests/benchmarks/...
-FETCHML_NATIVE_LIBS=1 go test ./tests/e2e/...
+# Run with native libraries
+go test -tags native_libs ./tests/benchmarks/...
+go test -tags native_libs ./tests/e2e/...
+
+# Run without native libraries (Go fallback)
+go test ./tests/benchmarks/...
 ```
 
 ### ASan Build
@@ -113,10 +125,10 @@ Run benchmarks to verify native libraries outperform pure Go:
 
 ```bash
 # Go implementation
-FETCHML_NATIVE_LIBS=0 go test -bench=. ./tests/benchmarks/
+go test -bench=. ./tests/benchmarks/
 
 # Native implementation
-FETCHML_NATIVE_LIBS=1 go test -bench=. ./tests/benchmarks/
+go test -tags native_libs -bench=. ./tests/benchmarks/
 ```
 
 ## Troubleshooting