M3: draw a GNOME-style title bar on Wayland (#553) (#1530)

GNOME's Wayland compositor draws no window frames (it offers no
zxdg_decoration_manager_v1), so winit drew its own fallback title bar,
which ignores GNOME's theme, dark mode and button layout. PdfCraft now
asks the compositor at launch (apps/pdfcraft/src/decorations.rs) and,
where it draws no frames, turns winit's frame off and makes the tab strip
the header bar, as in GNOME's own apps
(crates/ui-egui/src/window_controls.rs):

- Minimize, maximize/restore and close in Adwaita's style (round buttons,
  symbolic glyphs drawn in code, no new assets), in the order and on the
  side named by org.gnome.desktop.wm.preferences button-layout, read
  through gsettings; Fedora's default `appmenu:close` shows only close.
  Hidden in full screen.
- Resize zones along the window's edges and L-shaped corners, above the
  rest of the UI so a press there resizes instead of reaching a
  scrollbar; a hairline outlines the window while it isn't maximized.
- Preferences > Use system title bar (shown only where the app draws the
  frame) gives the window back winit's frame at once, without a restart
  (part of #1001). Named as in VectorCraft and PhotoCraft, but GNOME draws
  no title bars for apps, so on GNOME this is winit's basic frame, not
  GNOME's own; the tooltip says so. Saved as `system_title_bar`;
  `system-title-bar` on the control channel.
- PDFCRAFT_TITLEBAR=app|system overrides the detection.

KDE, Sway, Hyprland, COSMIC and X11 offer server-side decorations and
keep the frame their desktop draws; macOS and Windows are unchanged.

Not done: right-clicking the header bar doesn't open GNOME's window menu
(egui has no command for it), the window has no shadow or rounded
corners, the resize zones lie just inside the window rather than outside
it, and Windows still uses its system frame (the rest of #1001).

The new labels (Minimize, Maximize, Restore, Use system title bar and its
tooltip) were added to all 21 translation catalogs. These translations
have not been checked by anyone fluent in those languages and should be
reviewed. The catalogs' hashes in ATTRIBUTION.toml are updated.

Made with Claude Code (Claude Opus 5.5, medium effort). It passes the
workspace quality gates (fmt, clippy, cargo test --workspace, xtask
assets) and was checked by hand on Fedora 44 GNOME (light and dark,
maximized and not, the preference toggled live), but it has not been
exhaustively regression tested.

Co-authored-by: bmh129 <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>
Co-authored-by: Brandon Thomas <[email protected]>

docs/development.md

@@ -116,6 +116,7 @@ driver's shader compilation, and explicit `PDFCRAFT_RENDERER=wgpu` still disable
 | `WGPU_BACKEND` | Graphics backend; by default Windows uses Direct3D 12, falling back to OpenGL |
 | `WGPU_VALIDATION_INDIRECT_CALL` | `1` turns wgpu's check of indirect draw arguments back on. PdfCraft draws nothing indirectly and turns it off, since the compute shader the check needs fails to compile on some drivers (Metal on an Intel Iris Pro), which lost the device at start-up |
 | `PDFCRAFT_RENDERER` | `gl` starts with OpenGL (glow) and never loads wgpu; `wgpu` reports a wgpu failure instead of retrying with OpenGL; unset, wgpu is retried with OpenGL when it can't start (see [Renderer fallback](#renderer-fallback)) |
+| `PDFCRAFT_TITLEBAR` | Linux: `app` draws PdfCraft's own title bar (window buttons in the tab strip, in the order of GNOME's `button-layout`, and resize edges); `system` keeps the frame winit or the desktop draws; unset, PdfCraft draws its own when the Wayland compositor draws no frames (GNOME), and leaves it to the desktop otherwise (KDE, Sway, Hyprland, X11). Where PdfCraft draws it, Preferences ▸ Use system title bar switches back to winit's frame without a restart; `system` also hides that option |
 | `PDFCRAFT_BUILD_LABEL` | Build time: a label for a local or patched build (letters, digits, inner dots), shown after the version in `--version`, About and the log (`0.7.1 (titlebar)`). `packaging/linux/package.sh` also puts it in the file names and the .rpm/.deb release (`1.titlebar`), which upgrades over the release of the same version |
 | `CRAFT_FONTS_DIR` | Build time: a [craft-fonts](https://github.com/storytold/craft-fonts) checkout to embed (Japanese fonts) |
 | `PDFCRAFT_SYSTEM_FONTS` | `0` stops the desktop app from using an installed font for characters its embedded fonts lack (`cargo xtask screenshots` sets it) |