chore(ts7): adopt the TypeScript 7 native compiler (tsgo)

Make the editor packages compatible with, and benefit from, the native Go
compiler (TypeScript 7 / tsgo) while keeping the npm publish path on stable tsc.

- Add @typescript/native-preview (pinned 7.0.0-dev.20260624.1). tsgo coexists
  with typescript@6, which Next typegen and the IDE plugin still need until the
  TS 7.1 programmatic API ships.
- Fix two react-three-fiber JSX augmentations the native checker rejects but
  tsc tolerated:
  - viewer: map only LineBasicNodeMaterial (the one webgpu node material used as
    a JSX tag) instead of the whole three/webgpu namespace (TS2320/TS2590).
  - plane-box-select-tool: drop the redundant `IntrinsicElements extends
    ThreeElements` block — it duplicated R3F's global augmentation and, by
    referencing @react-three/fiber's ThreeElements directly, hit a bun peer-dep
    variant-directory duplicate under tsgo (TS2320). r3f.d.ts already covers
    those JSX intrinsics. Types-only — no runtime change.
- check-types -> tsgo --noEmit (editor, @repo/ui, editor app, ifc-converter app)
- emit-package dev watch -> tsgo --build --watch
- build/publish stay tsc --build (prepublishOnly + release.yml unchanged;
  emitted .d.ts is byte-identical to tsc output)
- bump next 16.2.6 -> 16.2.9

tsc remains the source of truth and fallback. Published artifacts unchanged.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/viewer/package.json

@@ -18,7 +18,7 @@
   ],
   "scripts": {
     "build": "tsc --build",
-    "dev": "tsc --build --watch",
+    "dev": "tsgo --build --watch",
     "prepublishOnly": "npm run build"
   },
   "peerDependencies": {