Migrate frontend from Svelte 5 to React 18

After hours of fighting Svelte 5's prop-reactivity through the
recursive Pane → SplitNode → LeafPane chain (props captured at
mount, never updated; context+getter pattern crashed; DOM-direct
workarounds created zombie-split click-intercept bugs), we
checkpointed the Svelte version (branch svelte-archive at e9015b2,
tarball at D:\archives\tiletopia-svelte-2026-05-22.tar.gz) and
rewrote the frontend in React.

Kept verbatim:
- All of src-tauri/ (Rust backend, Tauri config, icons)
- scripts/ (make-icon.py, release.sh)
- README.md, CLAUDE.md, memory.md
- src/lib/layout/tree.ts (pure TS — 43 tests still pass)
- src/ipc.ts (Tauri command wrappers)

Rewrote in React:
- src/App.tsx (top-level state via useState, OrchestrationProvider
  for descendants via React.Context)
- src/lib/layout/orchestration.tsx (React Context API for shared
  state — known-reliable reactivity, no Svelte 5 wall)
- src/lib/layout/Pane.tsx (recursive dispatcher)
- src/lib/layout/SplitNode.tsx (draggable gutter, local ratio state)
- src/lib/layout/LeafPane.tsx (toolbar + XtermPane)
- src/components/XtermPane.tsx (xterm.js wrapper, refs for callbacks)
- src/components/Notifications.tsx, Palette.tsx

Build: Vite + @vitejs/plugin-react. TypeScript strict. Same Tauri 2
config. Verified: pnpm check (clean), pnpm test (43/43 pass).
Not yet verified: pnpm tauri dev — that requires the Windows host.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

package.json

@@ -5,24 +5,25 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
-    "build": "vite build",
+    "build": "tsc -b && vite build",
     "preview": "vite preview",
-    "check": "svelte-check --tsconfig ./tsconfig.json",
     "test": "vitest run",
     "test:watch": "vitest",
+    "check": "tsc --noEmit",
     "tauri": "tauri"
   },
   "dependencies": {
     "@tauri-apps/api": "^2.0.0",
     "@xterm/addon-fit": "^0.10.0",
-    "@xterm/xterm": "^5.5.0"
+    "@xterm/xterm": "^5.5.0",
+    "react": "^18.3.0",
+    "react-dom": "^18.3.0"
   },
   "devDependencies": {
-    "@sveltejs/vite-plugin-svelte": "^4.0.0",
     "@tauri-apps/cli": "^2.0.0",
-    "@tsconfig/svelte": "^5.0.4",
-    "svelte": "^5.0.0",
-    "svelte-check": "^4.0.0",
+    "@types/react": "^18.3.0",
+    "@types/react-dom": "^18.3.0",
+    "@vitejs/plugin-react": "^4.3.0",
     "typescript": "^5.6.0",
     "vite": "^5.4.0",
     "vitest": "^2.0.0"