feat: upgrade to gnome 51

Adds GNOME Shell 51 to shell-version and moves the build onto the
GNOME 51 type packages.

- tabBar: pass orientation instead of vertical to St.BoxLayout. The vertical
  property was removed from St widgets in 51 (deprecated in 48); orientation
  exists in 48 and later, so this keeps 48-51 working. Verified against the
  installed St-51 typelib
- switch to @girs/gjs 5.5.0 and the -51 namespace packages (shell/st/meta/
  clutter plus gio/glib/gobject/gtk/gdk/adw/pango)
- drop @girs/gnome-shell 50 and the stale @girs/mtk-17 dependency. The
  umbrella is GNOME 50 only and pulls St-18 and Meta-18 types that clash
  with the -51 packages
- types/: hand-written declarations for the Shell JS modules imported here
  (extension.js, prefs.js, main.js). Upstream 51 types (51.0.0-alpha.1) are
  not published to npm yet
- TypeScript 6.0.3 rather than 7: typescript-eslint requires <6.1.0 and
  ts-jest requires <7
- eslint 10.12, @eslint/js 10.0.1, eslint-plugin-jsdoc 65.3.4,
  typescript-eslint 8.71.2 and jest 30.5.2 / ts-jest 29.4.14

tsconfig.json

@@ -10,14 +10,15 @@
     "target": "ES2022",
     "lib": [
       "ES2022"
-    ],
+    ]
   },
   "include": [
     "ambient.d.ts",
+    "types/**/*.d.ts",
     "prefs.ts",
     "src/**/*"
   ],
   "files": [
     "extension.ts"
-  ],
+  ]
 }