chore(deps): upgrade next to 16.3.0 and clean up the TypeScript toolchain (#6235)

Bumps next, @next/env and the @next/swc-* optional deps to 16.3.0 across the
root overrides, apps/sim, apps/docs and packages/emcn.

Two config notes worth keeping:

- `experimental.turbopackFileSystemCacheForBuild`'s default flipped false ->
  true for stable in 16.3.0, so our explicit `false` is now load-bearing rather
  than defensive. Without it this bump would have silently re-enabled a build
  cache measured 3.2x slower on this codebase (#6078). Comment updated to say so.
- `experimental.useTypeScriptCli: true` is now pinned. TypeScript 7 ships no
  JavaScript compiler API until 7.1, so Next's default checker cannot run and
  needs the project-local `tsc` CLI instead. 16.2.12 was silently skipping
  build-time type checking entirely because it detected @typescript/native-preview
  and short-circuited the stage ("Finished TypeScript in 138ms"); pinning the flag
  keeps that from drifting back.

TypeScript toolchain cleanup that the upgrade makes possible:

- Drop @typescript/native-preview from apps/sim and apps/docs. It was the
  pre-release channel for TS 7 and is superseded by typescript@7 (nightlies now
  ship as typescript@next), and its presence is what suppressed build type checks.
- Align packages/browser-protocol and packages/terminal-protocol from
  typescript ^5.7.3 to ^7.0.2 so every workspace is on one compiler version.

apps/sim keeps @typescript/typescript6 as a production dependency: the function
sandbox at app/api/function/execute dynamically imports the TS 6 compiler API to
transpile user code, and TS 7 has no API to replace it yet.

Build and dev were benchmarked 3x per version on a byte-identical tree; the
upgrade is performance-neutral (build median 100s -> 99s, dev:full warm 10s -> 9s).

apps/docs/package.json

@@ -31,7 +31,7 @@
     "fumadocs-openapi": "10.8.1",
     "fumadocs-ui": "16.8.5",
     "lucide-react": "^0.511.0",
-    "next": "16.2.12",
+    "next": "16.3.0",
     "next-themes": "^0.4.6",
     "react": "19.2.4",
     "react-dom": "19.2.4",
@@ -50,7 +50,6 @@
     "@types/node": "24.2.1",
     "@types/react": "^19.1.2",
     "@types/react-dom": "^19.0.4",
-    "@typescript/native-preview": "7.0.0-dev.20260707.2",
     "postcss": "^8.5.3",
     "tailwindcss": "^4.0.12",
     "typescript": "^7.0.2"