ci: desktop-smoke — czdev doctor+build+run on mac and linux

Matrix job installs SDL2/freetype/cmake, runs czdev doctor, builds
hello_cz, then headless-launches the emulator with SDL_VIDEODRIVER=dummy
and asserts it survives for 5s. Windows has a separate informational
job that surfaces the pending LVGL DLL rework (T08 in DESKTOP_DEV.md §4)
rather than failing silently.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/desktop-smoke.yml

@@ -0,0 +1,104 @@
+name: Desktop smoke (czdev + emulator + hello_cz)
+
+on:
+  push:
+    branches: [main, dev, ci/**]
+    paths:
+      - 'crates/czdev/**'
+      - 'emulator'
+      - 'examples/hello_cz/**'
+      - 'sdk/**'
+      - '.github/workflows/desktop-smoke.yml'
+  pull_request:
+    branches: [main]
+  workflow_dispatch:
+
+jobs:
+  smoke:
+    name: ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-24.04, macos-14]
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          submodules: recursive
+
+      - name: Install deps (Linux)
+        if: runner.os == 'Linux'
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+              build-essential cmake pkg-config \
+              libsdl2-dev libsdl2-image-dev libsdl2-mixer-dev libfreetype-dev \
+              xvfb
+
+      - name: Install deps (macOS)
+        if: runner.os == 'macOS'
+        run: |
+          brew install cmake pkg-config sdl2 sdl2_image sdl2_mixer freetype
+
+      - uses: dtolnay/rust-toolchain@stable
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
+      - name: czdev doctor
+        run: cargo run -p czdev --release -- doctor
+
+      - name: Build hello_cz (via czdev)
+        run: cargo run -p czdev --release -- build examples/hello_cz
+
+      - name: Headless emulator smoke (Linux)
+        if: runner.os == 'Linux'
+        env:
+          SDL_VIDEODRIVER: dummy
+          SDL_AUDIODRIVER: dummy
+        run: |
+          set -e
+          cargo run -p czdev --release -- run examples/hello_cz &
+          EMU_PID=$!
+          sleep 5
+          if ! kill -0 $EMU_PID 2>/dev/null; then
+            echo "::error::emulator exited before 5s"; exit 1
+          fi
+          kill $EMU_PID || true
+          wait $EMU_PID 2>/dev/null || true
+          echo "emulator ran for 5s — OK"
+
+      - name: Headless emulator smoke (macOS)
+        if: runner.os == 'macOS'
+        env:
+          SDL_VIDEODRIVER: dummy
+          SDL_AUDIODRIVER: dummy
+        run: |
+          set -e
+          cargo run -p czdev --release -- run examples/hello_cz &
+          EMU_PID=$!
+          sleep 5
+          if ! kill -0 $EMU_PID 2>/dev/null; then
+            echo "::error::emulator exited before 5s"; exit 1
+          fi
+          kill $EMU_PID || true
+          wait $EMU_PID 2>/dev/null || true
+          echo "emulator ran for 5s — OK"
+
+  # Windows smoke is gated on the LVGL DLL rework (see DESKTOP_DEV.md §4 / T08).
+  # Keep an informational job so CI surfaces the status rather than failing silently.
+  windows-todo:
+    runs-on: windows-latest
+    steps:
+      - name: Windows desktop dev is pending
+        shell: bash
+        run: |
+          echo "Windows support for the czdev loop requires the emulator's"
+          echo "LVGL DLL rework (see docs/DESKTOP_DEV.md §4). Tracked as T08."
+          echo "This job is informational; it does not fail the workflow."