Fix stray ^M characters in subprocess output when redirected to file

[Copilot]

Subprocesses using bare \r for in-place terminal progress updates (e.g. Downloading 50%\rDownloading 100%\n) pass those carriage returns through _PipeReaderThread._write() unchanged. When the output stream is not a terminal (file redirect, pipe), the \r chars survive into the written text, producing ^M-riddled output.

Changes

• craft_cli/messages.py — Normalize carriage returns in _PipeReaderThread._write() before line-splitting via a single re.sub pass:

  • \r\n / \r+\n (Windows endings, \r\r\n) → \n (no extra blank lines)
  • bare \r (in-place overwrites) → \n, so each update becomes its own line
  • b"\r" in data guard skips regex entirely for the common CR-free case

• tests/unit/test_messages_stream_cm.py — Two new tests as reproducers:

  • test_pipereader_carriage_returns: b"Step 1\rStep 2\rStep 3\n" → three clean lines, no \r
  • test_pipereader_windows_line_endings: b"line1\r\nline2\r\n" → two clean lines, no \r

# Before: \r passed through to the captured message
# text == ':: Initializing\rDone!'   ← stray ^M in file

# After: bare \r treated as line separator
# text[0] == ':: Initializing'
# text[1] == ':: Done!'