feat: detect external file renames and offer wikilink update via banner

When the app regains focus, checks git diff for renames (--diff-filter=R).
If renamed .md files are found, shows a non-blocking banner with "Update
wikilinks" and "Ignore" buttons. The update reuses the existing vault-wide
wikilink replacement logic from rename.rs.

New Tauri commands: detect_renames, update_wikilinks_for_renames.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/RenameDetectedBanner.test.tsx

@@ -0,0 +1,41 @@
+import { render, screen, fireEvent } from '@testing-library/react'
+import { describe, it, expect, vi } from 'vitest'
+import { RenameDetectedBanner } from './RenameDetectedBanner'
+
+describe('RenameDetectedBanner', () => {
+  const renames = [
+    { old_path: 'old-note.md', new_path: 'new-note.md' },
+    { old_path: 'folder/draft.md', new_path: 'folder/published.md' },
+  ]
+
+  it('renders nothing when renames is empty', () => {
+    const { container } = render(
+      <RenameDetectedBanner renames={[]} onUpdate={vi.fn()} onDismiss={vi.fn()} />
+    )
+    expect(container.firstChild).toBeNull()
+  })
+
+  it('shows banner with rename count', () => {
+    render(<RenameDetectedBanner renames={renames} onUpdate={vi.fn()} onDismiss={vi.fn()} />)
+    expect(screen.getByText(/2 files? renamed/i)).toBeInTheDocument()
+  })
+
+  it('shows Update wikilinks button', () => {
+    render(<RenameDetectedBanner renames={renames} onUpdate={vi.fn()} onDismiss={vi.fn()} />)
+    expect(screen.getByText('Update wikilinks')).toBeInTheDocument()
+  })
+
+  it('calls onUpdate when Update button clicked', () => {
+    const onUpdate = vi.fn()
+    render(<RenameDetectedBanner renames={renames} onUpdate={onUpdate} onDismiss={vi.fn()} />)
+    fireEvent.click(screen.getByText('Update wikilinks'))
+    expect(onUpdate).toHaveBeenCalledOnce()
+  })
+
+  it('calls onDismiss when Ignore button clicked', () => {
+    const onDismiss = vi.fn()
+    render(<RenameDetectedBanner renames={renames} onUpdate={vi.fn()} onDismiss={onDismiss} />)
+    fireEvent.click(screen.getByText('Ignore'))
+    expect(onDismiss).toHaveBeenCalledOnce()
+  })
+})

src/components/RenameDetectedBanner.tsx

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+import { ArrowsClockwise } from '@phosphor-icons/react'
+
+export interface DetectedRename {
+  old_path: string
+  new_path: string
+}
+
+interface RenameDetectedBannerProps {
+  renames: DetectedRename[]
+  onUpdate: () => void
+  onDismiss: () => void
+}
+
+export function RenameDetectedBanner({ renames, onUpdate, onDismiss }: RenameDetectedBannerProps) {
+  if (renames.length === 0) return null
+
+  const count = renames.length
+  return (
+    <div className="flex items-center gap-3 border-b border-border bg-accent/50 px-4 py-2 text-[13px]">
+      <ArrowsClockwise size={16} className="shrink-0 text-accent-foreground" />
+      <span className="flex-1 text-foreground">
+        {count} file{count !== 1 ? 's' : ''} renamed outside Laputa. Update wikilinks?
+      </span>
+      <button
+        className="shrink-0 cursor-pointer rounded-md bg-primary px-3 py-1 text-[12px] font-medium text-primary-foreground transition-colors hover:bg-primary/90"
+        onClick={onUpdate}
+      >
+        Update wikilinks
+      </button>
+      <button
+        className="shrink-0 cursor-pointer rounded-md border border-border bg-transparent px-3 py-1 text-[12px] font-medium text-muted-foreground transition-colors hover:bg-muted"
+        onClick={onDismiss}
+      >
+        Ignore
+      </button>
+    </div>
+  )
+}