Add ! bash mode with live shell output

[ZeroPoint95]

Bash mode via !

• model does NOT respond until next message

Changelog

• Run non-interactive ! commands in the conversation’s project.
• Show an amber $ prompt and live, literal shell output; retain output in chat history.
• Wait for the next message before the model responds. Keep shell commands separate from automated input and honor explicit denies.

Validation: terminal checks, bash regressions, and the full UI suite passed. make pr-ready remains blocked by three existing macOS session failures and a UI test race, reproduced on clean dev.

[AbirAbbas]

Taking this over to land it (Abir asked in the Slack thread). Everything in the description holds in the real binary:

• The command runs in the project, with the amber $.
• Output is live and literal, and stays in history after reopening, on both roads.
• The model waits and then sees the output with the next message.
• Denies are honored.
• An old dev engine and the v20 surface handle each other cleanly.

One blocker, fixed. A ! command skipped the critical floor: ! rm -rf /, mkfs, reboot and the fork bomb ran with no question in every posture, including --yolo, while the model's own bash call always asks and permissions.md promises it does. A critical ! command now puts the same question as a model call. Refused, interrupted or unattended, it does not run. Ordinary ! commands still run on Enter with no question. Four failing-first tests are included, and it was re-checked by hand on both roads.

Two smaller fixes:

• A ! row showed 30s · 0s left and kept running. It now counts against the runner's 10-minute timeout (30s / 10m).
• The manual now says ctrl+g cannot background a ! command. The chat was telling people it could.

Worth a follow-up, not blocking:

• A conversation that opens with a ! command is titled from the shell line (e.g. ! Pwd, ! Echo SKEW-1 > Skew1.txt). title.go could skip a message answered by a user_bash_ call.
• A manual search for "what does ! do" finds nothing, because the tokenizer drops !.
• The thinking flavour line draws above a running ! command.
• Answering "always" on the floor card writes the ordinary session bash memo. That matches the model's own floor card, but it may be worth leaving off here.

[AbirAbbas]

Verified in the real binary and merged by the takeover; see the comment above.