### What does this PR do?
The `sendPong` fix alone wasn't sufficient. The bug only manifests with
**wss:// through HTTP proxy** (not ws://), because only that path uses
`initWithTunnel` with a detached socket.
**Two bugs were found and fixed:**
1. **`sendPong`/`sendCloseWithBody` socket checks**
(`src/http/websocket_client.zig`): Replaced `socket.isClosed() or
socket.isShutdown()` with `!this.hasTCP()` as originally proposed. Also
guarded `shutdownRead()` against detached sockets.
2. **Spurious 1006 during clean close** (`src/http/websocket_client.zig`
+ `WebSocketProxyTunnel.zig`): When `sendCloseWithBody` calls
`clearData()`, it shuts down the proxy tunnel. The tunnel's `onClose`
callback was calling `ws.fail(ErrorCode.ended)` which dispatched a 1006
abrupt close, overriding the clean 1000 close already in progress. Fixed
by adding `tunnel.clearConnectedWebSocket()` before `tunnel.shutdown()`
so the callback is a no-op.
### How did you verify your code works?
- `USE_SYSTEM_BUN=1`: Fails with `Unexpected close code: 1006`
- `bun bd test`: Passes with clean 1000 close
- Full proxy test suite: 25 pass, 4 skip, 0 fail
- Related fragmented/close tests: all passing
---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
### What does this PR do?
Extract NO_PROXY checking logic from getHttpProxyFor into a reusable
isNoProxy method on the env Loader. This allows both fetch() and
WebSocket to check NO_PROXY even when a proxy is explicitly provided via
the proxy option (not just via http_proxy env var).
Changes:
- env_loader.zig: Extract isNoProxy() from getHttpProxyFor()
- FetchTasklet.zig: Check isNoProxy() before using explicit proxy
- WebSocket.cpp: Check Bun__isNoProxy() before using explicit proxy
- virtual_machine_exports.zig: Export Bun__isNoProxy for C++ access
- Add NO_PROXY tests for both fetch and WebSocket proxy paths
### How did you verify your code works?
Tests
---------
Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
### What does this PR do?
remove agent in global WebSocket (in node.js it uses dispatcher not
agent) add agent support in ws module (this actually uses agent)
### How did you verify your code works?
Tests
