feat(release): ship a Linux AppImage alongside the tarball (#55)

* feat(release): ship a Linux AppImage alongside the tarball

The Linux release was a bare, dynamically-linked binary built on
ubuntu-latest, so it only reliably ran on Ubuntu — Fedora/Arch users hit
missing/mismatched runtime libs. Add an AppImage that bundles the
x11/wayland/xkb/fontconfig/freetype libs so it launches across distros.

- bundle-appimage.sh: linuxdeploy populates an AppDir + deps, completions
  go beside the binary (usr/bin/completions, matching signature.rs's
  current_exe lookup), appimagetool packs it. Runs FUSE-less on CI.
- release.yml: new "Package Linux AppImage" step after the tarball,
  libfuse2/file added to the Linux deps, *.AppImage added to the upload
  list. The AppImage step avoids `rm -rf dist` so the tarball survives.
- README (en + zh): recommend the AppImage, keep the tarball as the bare
  fallback.

Note: glibc is not bundled, so ubuntu-latest still sets the glibc floor.

* fix(release): downscale AppImage icon to a resolution linuxdeploy accepts

linuxdeploy rejected the 1024x1024 app-icon.png (its valid list tops out at
512). Resize to 256x256 with ImageMagick's convert (added to the Linux apt
deps) before handing the icon to linuxdeploy.

---------

Co-authored-by: l0ng-ai <24760907+l0ng-ai@users.noreply.github.com>

.github/workflows/release.yml

@@ -50,7 +50,8 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y pkg-config cmake clang libxkbcommon-dev \
             libxkbcommon-x11-dev libfontconfig1-dev libfreetype6-dev \
-            libwayland-dev libx11-dev libxcb1-dev libzstd-dev libssl-dev
+            libwayland-dev libx11-dev libxcb1-dev libzstd-dev libssl-dev \
+            libfuse2 file imagemagick
 
       - uses: dtolnay/rust-toolchain@stable
         with:
@@ -89,6 +90,14 @@ jobs:
         working-directory: tty7
         run: bash .github/scripts/bundle-linux.sh "${{ matrix.target }}" "${{ matrix.arch }}"
 
+      # AppImage bundles the x11/wayland/xkb/font libs so it runs on Fedora/Arch/
+      # etc., not just Ubuntu. Kept separate from the tarball step so the tarball
+      # still ships even if AppImage tooling changes upstream.
+      - name: Package Linux AppImage
+        if: matrix.os == 'linux'
+        working-directory: tty7
+        run: bash .github/scripts/bundle-appimage.sh "${{ matrix.target }}" "${{ matrix.arch }}"
+
       - name: Package Windows installer + zip
         if: matrix.os == 'windows'
         working-directory: tty7
@@ -104,3 +113,4 @@ jobs:
             tty7/dist/*.tar.gz
             tty7/dist/*.zip
             tty7/dist/*-setup.exe
+            tty7/dist/*.AppImage