M14: Arabic and Hebrew file names render in the tab strip, recent files and Properties (#285)

A tab named in Arabic showed replacement boxes: no interface font had the
glyphs, and egui joins the letters of a right-to-left word but places the
runs in logical order.

- Fonts: the interface takes `Arab` faces from the craft-fonts build input
  (also on wasm), and on desktop adds one font already installed on the
  machine as the last fallback of every family. It is read at runtime, never
  embedded; PDFCRAFT_SYSTEM_FONTS=0 turns it off and `cargo xtask screenshots`
  sets that. AGENTS.md §1.4 records the rule.
- Order: bidi::visual puts single-line text in display order with a
  left-to-right base, used for the painted tab label and hover text, the
  recent-files name and path, and the Properties File and Location rows.
  Accessibility names keep the logical text.

misc.rtl-ui stays planned: multi-line text, text input and a mirrored layout
are not done.

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

docs/development.md

@@ -31,3 +31,4 @@ covers every target starting with it (`pdfcraft*=debug`). The logger is
 | `WGPU_POWER_PREF` | GPU choice; by default PdfCraft prefers the low-power (integrated) GPU |
 | `WGPU_BACKEND` | Graphics backend; by default Windows uses Direct3D 12, falling back to OpenGL |
 | `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) |