Installed the normal plan proposal handler in print mode, persisted the resolved plan artifact, and silently stopped the completed planning turn for later review.
Shared plan proposal validation with interactive mode and added regression coverage.
Fixes#6017
Applied the startup plan default before headless prompts and persisted the mode for later interactive review.
Added regression coverage for the exact -p startup path.
Fixes#6017
- Wrote a one-shot stderr working indicator before text print-mode prompts wait on the model.
- Covered pending text/json print-mode behavior with focused tests.
Fixes#4901