fix: bundle SDK+zod in react-with-deps (was byte-identical to ./react) (#539)

* chore: remove dead ./react-with-deps export (copy-paste bug from #221)

The react-with-deps build entry was introduced in PR #221 (e078250a) as a
sibling to app-with-deps for CDN/unpkg no-bundler use. But its external
array was duplicated without editing — it never dropped @modelcontextprotocol/sdk
from externals, so it has shipped byte-identical to ./react for 10 releases
(v0.3.1 → v1.2.0).

After #534 merged, both entries use ['react', 'react-dom', ...PEER_EXTERNALS]
— still identical, just smaller.

Delete rather than fix: React apps always use a bundler; the CDN/unpkg
use case (HTML-string apps like qr-server) doesn't apply to React hooks.
Zero consumers verified (examples/docs/tests/plugins).

* fix: bundle SDK+zod in react-with-deps (keep React external)

Reverts the deletion from the previous commit and applies the actual fix.

The react-with-deps external array was copy-pasted in PR #221 without
dropping PEER_EXTERNALS — now it mirrors app-with-deps: bundles
@modelcontextprotocol/sdk + zod for CDN/import-map consumers.

React and react-dom MUST remain external — bundling them would cause
dual-React-instance hooks errors. Consumer provides them via import map.

Before: index.js 26KB == react-with-deps.js 26KB (identical MD5)
After:  index.js 26KB != react-with-deps.js 323KB (SDK+zod bundled)

build.bun.ts

@@ -54,7 +54,7 @@ await Promise.all([
   }),
   buildJs("src/react/index.tsx", {
     outdir: "dist/src/react",
-    external: ["react", "react-dom", ...PEER_EXTERNALS],
+    external: ["react", "react-dom"],
     naming: { entry: "react-with-deps.js" },
   }),
   buildJs("src/server/index.ts", {