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>

tsconfig.json

@@ -1,20 +1,7 @@
 {
-  "extends": "@tsconfig/svelte/tsconfig.json",
-  "compilerOptions": {
-    "target": "ESNext",
-    "useDefineForClassFields": true,
-    "module": "ESNext",
-    "resolveJsonModule": true,
-    "allowSyntheticDefaultImports": true,
-    "esModuleInterop": true,
-    "moduleResolution": "Bundler",
-    "strict": true,
-    "isolatedModules": true,
-    "skipLibCheck": true,
-    "noUnusedLocals": false,
-    "noUnusedParameters": false,
-    "verbatimModuleSyntax": true
-  },
-  "include": ["src/**/*.ts", "src/**/*.svelte"],
-  "references": [{ "path": "./tsconfig.node.json" }]
+  "files": [],
+  "references": [
+    { "path": "./tsconfig.node.json" },
+    { "path": "./tsconfig.app.json" }
+  ]
 }