SH3006: The build's link is busy, closed, or answered what shuyi can't read

Class: operation, exit code 1.

attach reached the build and said hello, then the link failed: another client is attached already (a build takes one at a time), the build closed the link or quit while answering, it didn't answer in time (a build suspended for long, say), or it answered something this shuyi can't read. An MCP session attached over the link ends with it.

How to fix it. Detach the other client (stop its attach, or the agent's session holding it), or start the build again, then attach again.

For example:

attach: error[SH3006]: another client is attached to the build at 127.0.0.1:7357