fix(proxy): preserve fetch semantics through the proxy adapter

Addresses review round 4 on #2099 — three posted comments and three suppressed
ones, all valid.

- A rebuilt Response reported `url: ""`, `redirected: false`, and
  `type: "default"` even after undici followed a redirect: a fetch-contract
  regression visible only to proxy users, and one `core/auth/endpointOverrides.ts`
  explicitly guards against by declining to rebuild at all. This adapter has no
  such choice — the response arrives from the wrong realm — so it now reinstates
  the three with `defineProperty`.

- Normalizing a `Request` input dropped every option the Request itself carried
  beyond method/headers/body/signal. Most visibly `redirect`: a
  `new Request(url, { redirect: "manual" })` started following redirects instead
  of surfacing them. All of them are now carried through, with an explicit
  `init` still winning per the fetch contract.

  Both are covered by tests driving a real redirect through a real proxy, and
  both were confirmed to fail without the fix.

- `@modelcontextprotocol/ext-apps` was added only to the CLI's `external` list.
  AGENTS.md requires every root-declared runtime dependency in all three, since
  which client reaches it is a function of what `core/` imports rather than of
  the client's own code. Added to the web runner and TUI lists too.

- The `BUNDLED_CLIENTS` test compared the hard-coded list against a hard-coded
  copy of itself, so a new tsup-bundled client would have left it green while
  going unchecked. It now discovers clients from disk (a client is tsup-bundled
  iff it ships a tsup config) and compares. Verified it fails when a stub client
  is added.

- AGENTS.md's project tree still described `core/mcp/node/` as only the stdio
  transport factory; it now carries `proxyFetch.ts` and its role.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JTHVxSu8AUgHRLvo1ntZ8H
Signed-off-by: cliffhall <cliff@futurescale.com>

AGENTS.md

@@ -169,7 +169,11 @@ v2/main/
 │   │   │                               #   server.json parser, strategy registry + well-known
 │   │   │                               #   paths, strategy-agnostic merge. Pure/isomorphic;
 │   │   │                               #   used by the web file-upload path + /api/import-source.
-│   │   ├── node/                       # Node stdio transport factory
+│   │   ├── node/                       # Node stdio transport factory, plus proxyFetch.ts
+│   │   │                               #   (the shared HTTPS_PROXY/HTTP_PROXY/NO_PROXY
+│   │   │                               #   fetch every Node client installs as its
+│   │   │                               #   `environment.fetch`, and the web backend as the
+│   │   │                               #   createTransportNode default — #2067)
 │   │   ├── remote/                     # Browser HTTP/SSE transport + remote logger/fetch
 │   │   │   └── node/                   # Hono-based remote server backend (used by remote/ above)
 │   │   └── state/                      # InspectorClient state stores consumed by core/react/