fix(trail): sharpen the overwrite guard's message and pass work with no project trail

Commit

peyton-altyesterday
  • Give the concrete 'entire trail update <repo>/<n>' command when the number is the branch's change number (the docs promised one).
  • Pass when the branch's work has no project parent: it is on no project trail, so #N cannot be mistaken for it, and the suggested no-selector update would have failed.
  • Sanitize the trail ID in the refusal like every other server string.
  • Reuse trailBranchFlag.

Co-Authored-By: Claude Opus 5.5 noreply@anthropic.com Claude-Session: https://claude.ai/code/session_01XJeHKftfKHD7hSi6ZxJww8 Entire-Checkpoint: 01M6KVGKBFF80HYV5QTJG4SH4B