`POST /api/sessions/:id/run` had no adopted gate, so while the wrapper had no
attached PTY it spawned `claude -p --dangerously-skip-permissions <prompt>`
in /tmp, a launch every other adopted route refuses.
The route answers INVALID_INPUT, and `runPrompt()` refuses too, which also
covers the legacy `sendInput()` path and leaves no direct spawn in Session
that an adopted session can reach.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>