In Node.js, process.nextTick always runs before I/O callbacks. The HTTP
client uses nextTick to defer emitFreeNT (which returns sockets to the
agent's free pool). In Deno, I/O can interleave with nextTick, so a
server FIN may arrive before emitFreeNT runs, making the socket
non-writable.

Fix by checking socket.destroyed instead of !socket.writable in the
agent's 'free' handler. A socket that received a server FIN but hasn't
been destroyed yet can still be pooled — it will be cleaned up by the
'close' listener installed in installListeners.

Enables test-http-agent-keepalive.js in the compat suite.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

The globalAgent was exported as a static value, so assigning
http.globalAgent = newAgent had no effect on subsequent requests.

Fix by:
- Making globalAgent a mutable let export in _http_agent.js
- Adding setGlobalAgent() helper
- Using getter/setter on the http default export
- Accessing globalAgent via httpAgent.globalAgent in _http_client.js
  (dynamic lookup instead of static import binding)

Enables test-http-client-override-global-agent.js in compat suite.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Node.js spreads the URL object (...url) into the options so that
user-added properties (like headers) are preserved. Deno only extracted
known URL properties, losing any user extensions.

Enables test-http-client-request-options.js in compat suite.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

When the server emits 'connect' or 'upgrade', the socket should be
fully detached from the HTTP server — all server-added listeners
removed. Previously Deno left them attached, causing listener count
assertions to fail and the socket to remain under server control.

Match Node.js behavior by removing data, end, close, drain, error,
and timeout listeners before emitting the event. Also remove the
Deno-specific ConnectionsList tracking listener and pop the socket
from the connections list.

Enables test-http-connect.js and test-http-connect-req-res.js in the
compat suite.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

Add strict content-length validation to OutgoingMessage:
- In write_(): throw if bytes written exceed content-length (or don't
  match on end)
- In end(): throw if total bytes written doesn't match content-length
- Add ERR_HTTP_CONTENT_LENGTH_MISMATCH error class

Enables test-http-content-length-mismatch.js in compat suite.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>

…ket guard

- Implement ERR_HTTP_CONTENT_LENGTH_MISMATCH validation in write_() and
  end() for strictContentLength mode
- Tighten agent free socket guard: use socket.destroyed for early exit,
  but still check !socket.writable before assigning to queued requests
  (prevents handing half-closed sockets to new requests)

Enables test-http-content-length-mismatch.js in compat suite.

Co-Authored-By: Claude Opus 4.6 (1M context) <[email protected]>