feat: initial implementation of mousefree

Keyboard-driven mouse navigation overlay for Wayland using
wlr-layer-shell and wlr-virtual-pointer. Two-key grid selection,
click/double-click/right-click/drag, three-tier cursor nudge
(hjkl/HJKL/Ctrl+hjkl), and scroll passthrough.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -0,0 +1,48 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rust: ["1.75", stable]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libwayland-dev
+      - run: cargo test
+
+  clippy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: clippy
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y libwayland-dev
+      - run: cargo clippy --all-targets -- -D warnings
+
+  fmt:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
+      - run: cargo fmt --check