feat(core): honor HTTPS_PROXY/HTTP_PROXY/NO_PROXY in the Node transport (closes #1563)

Wrap the Node transport's fetch with an undici EnvHttpProxyAgent dispatcher
when a standard proxy env var is set, so the CLI and web backend can reach
remote MCP servers through corporate proxies with zero new flags. undici is
imported lazily (only when a proxy var is present) and added as a dependency
at the repo root and in the CLI client; a missing undici raises an actionable
error. Documents the behavior and dependency in the CLI README.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S3fTN8H3R8YV4yUGvZjYnX

package.json

@@ -72,6 +72,7 @@
     "open": "^10.2.0",
     "pino": "^9.14.0",
     "react": "^19.2.4",
+    "undici": "^8.5.0",
     "vite": "^8.0.0",
     "yaml": "^2.9.0",
     "zod": "^4.3.6",