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>

vite.config.ts

@@ -1,9 +1,9 @@
 /// <reference types="vitest" />
 import { defineConfig } from "vite";
-import { svelte } from "@sveltejs/vite-plugin-svelte";
+import react from "@vitejs/plugin-react";
 
-export default defineConfig(async () => ({
-  plugins: [svelte()],
+export default defineConfig({
+  plugins: [react()],
   clearScreen: false,
   server: {
     port: 1420,
@@ -19,6 +19,6 @@ export default defineConfig(async () => ({
   },
   test: {
     environment: "node",
-    include: ["src/**/*.test.ts"],
+    include: ["src/**/*.test.ts", "src/**/*.test.tsx"],
   },
-}));
+});