Noticed when enabling the goleak checker in chatd:
```
=== FAIL: coderd/x/chatd (0.00s)
PASS
goleak: Errors on successful test run: found unexpected goroutines:
[Goroutine 108179 in state select, with github.com/coder/coder/v2/tailnet.(*Conn).AwaitReachable on top of the stack:
github.com/coder/coder/v2/tailnet.(*Conn).AwaitReachable(0x2c35e171d760, {0x74b37a8?, 0x2c35f6886330?}, {{0x0?, 0x0?}, {0x2c35def838c0?}})
/home/runner/work/coder/coder/tailnet/conn.go:647 +0x2ae
github.com/coder/coder/v2/codersdk/workspacesdk.(*agentConn).AwaitReachable(0x2c35e4f18440, {0x74b37e0?, 0x2c35f45680a0?})
/home/runner/work/coder/coder/codersdk/workspacesdk/agentconn.go:172 +0x12b
github.com/coder/coder/v2/codersdk/workspacesdk.(*agentConn).apiRequest.(*agentConn).apiClient.func1({0x74b37e0, 0x2c35f45680a0}, {0x61a8946?, 0x60fa2a0?}, {0x2c35e0af7380, 0x2b})
/home/runner/work/coder/coder/codersdk/workspacesdk/agentconn.go:1381 +0x212
net/http.(*Transport).dial(0x2c35e0af6210?, {0x74b37e0?, 0x2c35f45680a0?}, {0x61a8946?, 0xa0e255?}, {0x2c35e0af7380?, 0xa1456f?})
/home/runner/work/_temp/mise-data/installs/go/1.26.4/src/net/http/transport.go:1307 +0xd2
net/http.(*Transport).dialConn(0x2c35f8d8b380, {0x74b37e0, 0x2c35f45680a0}, {{}, 0x0, {0x2c35fc5a3e50, 0x4}, {0x2c35e0af7380, 0x2b}, 0x0}, ...)
/home/runner/work/_temp/mise-data/installs/go/1.26.4/src/net/http/transport.go:1815 +0x847
net/http.(*Transport).dialConnFor(0x2c35f8d8b380, 0x2c35e287a580)
/home/runner/work/_temp/mise-data/installs/go/1.26.4/src/net/http/transport.go:1648 +0xd2
net/http.(*Transport).startDialConnForLocked.func1()
/home/runner/work/_temp/mise-data/installs/go/1.26.4/src/net/http/transport.go:1629 +0x35
created by net/http.(*Transport).startDialConnForLocked in goroutine 107872
/home/runner/work/_temp/mise-data/installs/go/1.26.4/src/net/http/transport.go:1628 +0x112
Goroutine 108180 in state select, with github.com/cenkalti/backoff/v4.(*Ticker).run on top of the stack:
github.com/cenkalti/backoff/v4.(*Ticker).run(0x2c35f8517860)
/home/runner/go/pkg/mod/github.com/cenkalti/backoff/v4@v4.3.0/ticker.go:70 +0x13f
created by github.com/cenkalti/backoff/v4.NewTickerWithTimer in goroutine 108179
/home/runner/go/pkg/mod/github.com/cenkalti/backoff/v4@v4.3.0/ticker.go:49 +0x16c
]
FAIL github.com/coder/coder/v2/coderd/x/chatd 126.492s
```
Closes https://github.com/coder/internal/issues/1595