Sublime-style Build-n versioning + About box

Build n = commit count, baked at build time into a gitignored
version.gen.ts (postinstall + all build scripts regenerate it). About
lives in the macOS app menu and as a footer row in the options popover
(the cross-platform path), showing build, commit, date and engines.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ui/src/app/tab-bar/tab-bar.ts

@@ -1,5 +1,6 @@
 import { Component, ElementRef, effect, inject, signal, viewChild } from '@angular/core';
 import { NgIcon } from '@ng-icons/core';
+import { BRANDING } from '@shared/branding';
 import type { AccentTone } from '@shared/types';
 import { PanelsService } from '../panels.service';
 import { IS_MAC_CHROME } from '../platform';
@@ -339,6 +340,14 @@ const CONCURRENCY_CHOICES = [2, 3, 4, 6, 8] as const;
               </button>
             </div>
           </div>
+
+          <!-- about footer -->
+          <button
+            (click)="showAbout()"
+            class="mt-3 w-full border-t border-border pt-2 text-center text-[11px] text-muted-foreground hover:text-foreground"
+          >
+            {{ appName }} · {{ buildLabel }}
+          </button>
         </div>
       }
     </div>
@@ -350,6 +359,8 @@ export class TabBar {
   private readonly rpc = inject(RpcService);
   readonly settingsOpen = signal(false);
   readonly isMacChrome = IS_MAC_CHROME;
+  readonly appName = BRANDING.appName;
+  readonly buildLabel = BRANDING.buildLabel;
   readonly themes = THEMES;
   readonly darkTones = DARK_TONES;
   readonly accents = ACCENTS;
@@ -392,6 +403,10 @@ export class TabBar {
     void this.rpc.request.openConnectionManager({});
   }
 
+  showAbout(): void {
+    void this.rpc.request.showAbout({});
+  }
+
   async pickEditorApp(): Promise<void> {
     const res = await this.rpc.request.pickEditorApp({});
     if (res.ok && res.path) this.settings.setEditorApp(res.path);