The spinner goroutine was writing carriage-return + status text to
os.Stdout every 100ms. In the non-interactive TTY path, the child
process also writes directly to os.Stdout, causing both writers to
race on the same file descriptor. The \r emitted by the spinner
resets the cursor to column 0 mid-line, corrupting and truncating
the child process output.
Fix by writing all spinner/status output to os.Stderr, which is the
standard Unix convention for diagnostic and status messages. This is
also consistent with how progress.go and ShowWarning already behave.
https://claude.ai/code/session_012jMiRSS4Jx9Bs7a2F4S6KN
Co-authored-by: Claude <noreply@anthropic.com>
* provide package blocked feedback in proxy mode
* update test case & clear status on block
* refactor reporting
* clearStatus on `continueExecution`
* set spinnerChan to nil
* add sync for spinner
