fix(acp): preserve bash output after terminal release

[frostming]

Bash commands can finish with a blank output body in Paseo: Bub releases the client terminal before sending the completion update, and Paseo discards the terminal buffer and ignores string rawOutput. Completion updates now include a text snapshot of the result, so output remains visible after terminal release.

The ACP bash tool now takes command instead of cmd and removes the optional title argument. Live updates and history replay use the command as the title and show only output in the body. Running commands still attach the client terminal.

This PR is stacked on #69 and targets fix/bub-instance-tools; merge that PR first.

Validation:

• All 129 ACP tests pass, including a regression that deletes terminal buffers on release and checks normal, multiline, and empty output.
• Ruff lint and formatting checks pass.
• The local bub-dev environment loads the updated editable package; Paseo UI verification after restarting Bub remains pending.