Add Unwrap() to StatusWriter so http.ResponseController.SetWriteDeadline
can reach the underlying net.Conn through the middleware wrapper. Without
this, the agent's 20s WriteTimeout killed blocking process output
connections.
Also add 30s headroom to the write deadline in handleProcessOutput so
the response can be written after a full-duration blocking wait.
On the tool layer, waitForProcess and the process_output tool now try a
non-blocking snapshot on any error, not just context timeout. Transport
errors (like the WriteTimeout EOF) previously returned with no process
ID and no recovery path. Now if the process finished, the result is
returned transparently. If still running, the error includes the process
ID and tells the agent to use process_output.
Replace the 200ms polling loop in chatd's execute and
process_output tools with server-side blocking via sync.Cond
on HeadTailBuffer.
The agent's GET /{id}/output endpoint accepts ?wait=true to
block until the process exits or a 5-minute server cap expires.
The process_output tool blocks by default for 10s (overridable
via wait_timeout), and falls back to a non-blocking snapshot on
timeout. The execute tool's foreground path makes a single
blocking call instead of polling.
Related #23316
The ampersand detection treated bash's pipe-stderr operator (|&)
as a trailing & for backgrounding, stripping it and producing a
broken pipe command. Also adds tests for execute.go and chatloop
context limit helpers, covering previously untested edge cases.