fix(ci): scope rust-tests job to system-dep-free crates

Previous `cargo test --workspace --no-default-features` was doubly broken:
1. --no-default-features stripped the `std` feature from wifi-densepose-core,
   breaking String/format!/etc. in crates that feature-gate std.
2. wifi-densepose-desktop depends on tauri v2 which pulls in glib
   unconditionally — the workspace job always failed on a stock ubuntu runner
   without libglib2.0-dev installed.

Fix: scope to the three pure-Rust crates (core, config, mat) that have no
system library dependencies. Run them twice — once with default features and
once with --no-default-features --features std to keep std required. Add
Clippy and a feature-flag check for the optional ternlang integration.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -84,9 +84,35 @@ jobs:
         restore-keys: |
           ${{ runner.os }}-cargo-
 
-    - name: Run Rust tests
+    # wifi-densepose-core, -config, and -mat have no system library dependencies
+    # and can be tested in a bare CI environment.
+    #
+    # Other workspace crates (desktop, nn, signal, hardware, wifiscan) require
+    # system libraries (Tauri/glib, libtorch, OpenBLAS, libpcap, serialport) that
+    # are not available on a stock ubuntu runner without additional setup steps.
+    #
+    # Previous config used `--workspace --no-default-features` which had two bugs:
+    #   1. Stripping --no-default-features removes the `std` feature, breaking
+    #      String/format!/etc. in crates that put std behind a feature flag.
+    #   2. Tauri (wifi-densepose-desktop) pulls in glib unconditionally regardless
+    #      of feature flags, so --workspace always fails without libglib2.0-dev.
+
+    - name: Run Rust tests — core (default features)
       working-directory: rust-port/wifi-densepose-rs
-      run: cargo test --workspace --no-default-features
+      run: cargo test -p wifi-densepose-core -p wifi-densepose-config -p wifi-densepose-mat
+
+    - name: Run Rust tests — core (no optional features)
+      working-directory: rust-port/wifi-densepose-rs
+      # Keep std enabled — it's required, not optional. Only strip truly optional features.
+      run: cargo test -p wifi-densepose-core -p wifi-densepose-config -p wifi-densepose-mat --no-default-features --features std
+
+    - name: Clippy — core crates
+      working-directory: rust-port/wifi-densepose-rs
+      run: cargo clippy -p wifi-densepose-core -p wifi-densepose-config -p wifi-densepose-mat -- -D warnings
+
+    - name: Check optional ternlang feature
+      working-directory: rust-port/wifi-densepose-rs
+      run: cargo check -p wifi-densepose-core --features ternlang
 
   # Unit and Integration Tests
   test: