v1.2: overwrite confirm, transfer speed/ETA, settings + themes, fused macOS titlebar

- Overwrite confirmation: name-collision detection before enqueue; dialog shows
  source vs destination (size, mtime, 'newer' badge) with per-item Skip/Replace
  and batch Skip all / Replace all; type mismatches auto-skip with a toast;
  cancel aborts the whole operation
- Transfer speed + ETA: UI computes smoothed bytes/sec from progress deltas
  (callback bus makes deltas meaningful); shown in the expanded queue rows and
  the status-bar summary; unit follows the speed-unit setting
- Settings: bun-side SettingsStore (settings.json, 0600, atomic) + get/save RPC;
  SettingsService; gear popover on the tab row (theme segmented control, speed
  unit); persisted across restarts
- Light theme: data-theme on <html> drives token overrides; absent = follow OS
- macOS fused titlebar: hiddenInset + trafficLightOffset, tab row becomes the
  draggable titlebar (app-region drag/no-drag classes); other platforms keep a
  separate titlebar (gated by a platform value injected via window preload)
- README: known-issues note for the upstream Bun/Electrobun FFI crash

Verified: tsc + ui build clean; SettingsStore roundtrip + 0600 headless;
app boots and the UI fetches settings over RPC at startup.

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

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

@@ -1,7 +1,9 @@
 import { Component, computed, inject } from '@angular/core';
 import { NgIcon } from '@ng-icons/core';
 import type { TransferSnapshot } from '@shared/types';
+import { formatSpeed } from '../format';
 import { PanelsService } from '../panels.service';
+import { SettingsService } from '../settings.service';
 import { TransfersService } from '../transfers.service';
 
 @Component({
@@ -20,7 +22,7 @@ import { TransfersService } from '../transfers.service';
         @if (transfers.currentJob(); as job) {
           <ng-icon name="mynaSpinner" size="0.8rem" class="shrink-0 animate-spin text-primary" />
           <span class="truncate">
-            Copying {{ job.name }} · {{ percent(job) }}%
+            Copying {{ job.name }} · {{ percent(job) }}%{{ speedSuffix(job) }}
             @if (transfers.queuedCount(); as queued) {
               · {{ queued }} queued
             }
@@ -57,10 +59,16 @@ import { TransfersService } from '../transfers.service';
 export class StatusBar {
   readonly transfers = inject(TransfersService);
   readonly panels = inject(PanelsService);
+  readonly settings = inject(SettingsService);
   readonly activePanel = computed(() => this.panels.get(this.panels.activeSide()));
 
   percent(job: TransferSnapshot): number {
     if (!job.totalBytes) return 0;
     return Math.min(100, Math.round((job.doneBytes / job.totalBytes) * 100));
   }
+
+  speedSuffix(job: TransferSnapshot): string {
+    const speed = this.transfers.speeds().get(job.id);
+    return speed ? ` · ${formatSpeed(speed, this.settings.speedUnit())}` : '';
+  }
 }