llvm(py): introduce BuildCtx + trace hub; refactor if-merge prepass + PHI wiring into module; unify logs; ctx-enable compare/ret/call/boxcall/externcall/typeop/newbox/safepoint; curated smoke option for if-merge; README updates; keep behavior stable

.github/workflows/vm-legacy-build.yml

@@ -0,0 +1,29 @@
+name: vm-legacy-build
+
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - 'src/**'
+      - 'Cargo.toml'
+      - '.github/workflows/vm-legacy-build.yml'
+
+jobs:
+  build-vm-legacy:
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache Rust build
+        uses: Swatinem/rust-cache@v2
+        with:
+          cache-targets: true
+
+      - name: Build with vm-legacy + interpreter-legacy (compile check only)
+        run: cargo build --release --features vm-legacy,interpreter-legacy
+