fix(ui): adapt to TypeScript 6, Vite 8, @vitejs/plugin-react 6 majors

Three incompatibilities surfaced after the dev-tooling group bump:

1. tsconfig.app.json — TypeScript 6 deprecates `baseUrl`. Since TS 5
   `paths` is resolved relative to the tsconfig dir, so drop `baseUrl`
   entirely and make the `@/*` path explicit (`./src/*`).

2. vite.config.ts — Vite 8 / Rollup 4's `manualChunks` type narrowed to
   only accept the function form in some overloads. Convert from the
   `Record<string, string[]>` shape to the function form, matching on
   `node_modules/<pkg>` paths.

3. Test polyfills — TypeScript 6 / @types/node changes remove the
   ambient `global` identifier. Switch both jsdom ResizeObserver
   polyfills to `globalThis`, which is the standard JS spelling.

Local verification (Vite 8.0.9 + Vitest 4.1.5 + TypeScript 6.0.3):
  - npm run typecheck  — clean
  - npm test           — 52/52 passing
  - npm run build      — initial chunk 441 KB (budget 580 KB)

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

Author: aksOps

ui/src/components/layout/__tests__/ThemeToggle.test.tsx

@@ -5,8 +5,8 @@ import { ThemeToggle } from "../ThemeToggle";
 import { useUIStore } from "@/stores/ui";
 
 // Polyfills for Radix dropdown in jsdom
-if (!(global as any).ResizeObserver) {
-  (global as any).ResizeObserver = class { observe() {} unobserve() {} disconnect() {} };
+if (!(globalThis as any).ResizeObserver) {
+  (globalThis as any).ResizeObserver = class { observe() {} unobserve() {} disconnect() {} };
 }
 if (!(Element.prototype as any).scrollIntoView) {
   (Element.prototype as any).scrollIntoView = () => {};

ui/src/components/notes/__tests__/TreeDrawer.test.tsx

@@ -7,8 +7,8 @@ import { server } from "@/test/msw";
 import { TreeDrawer } from "../TreeDrawer";
 
 // Polyfills for jsdom that shadcn Sheet (Radix) may need:
-if (!(global as any).ResizeObserver) {
-  (global as any).ResizeObserver = class { observe() {} unobserve() {} disconnect() {} };
+if (!(globalThis as any).ResizeObserver) {
+  (globalThis as any).ResizeObserver = class { observe() {} unobserve() {} disconnect() {} };
 }
 if (!(Element.prototype as any).scrollIntoView) {
   (Element.prototype as any).scrollIntoView = () => {};

ui/tsconfig.app.json

@@ -17,8 +17,7 @@
     "noUnusedParameters": true,
     "noFallthroughCasesInSwitch": true,
     "noUncheckedSideEffectImports": true,
-    "baseUrl": ".",
-    "paths": { "@/*": ["src/*"] }
+    "paths": { "@/*": ["./src/*"] }
   },
   "include": ["src"]
 }

ui/vite.config.ts

@@ -16,10 +16,10 @@ export default defineConfig({
     sourcemap: false,
     rollupOptions: {
       output: {
-        manualChunks: {
-          "markdown": ["markdown-it", "shiki"],
-          "graph": ["d3-force"],
-          "editor": ["codemirror", "@codemirror/view", "@codemirror/state", "@codemirror/commands", "@codemirror/lang-markdown"],
+        manualChunks(id) {
+          if (/node_modules[\\/](markdown-it|shiki)[\\/]/.test(id)) return "markdown";
+          if (/node_modules[\\/]d3-force[\\/]/.test(id)) return "graph";
+          if (/node_modules[\\/](codemirror|@codemirror[\\/])/.test(id)) return "editor";
         },
       },
     },