Cloud Mode: warn on shell-command first query and recover from Ctrl-C state [REMOTE-1533]

[warp-dev-github-integration]

Description

Two Cloud Mode UX fixes from user feedback in REMOTE-1533:

1. Warning toast when the first query is a shell command

When composing the first query for a cloud agent run in V1 cloud mode (without CloudModeInputV2) with the input switched to shell mode, submitting silently fell through to the shell-execution path on the deferred cloud-mode terminal that has no PTY to run against. The user got no signal that nothing happened.

Now we surface a clear error toast (“Cloud agent conversations need an AI prompt as the first query…”) and short-circuit the submission instead. Implemented as a new should_warn_cloud_mode_first_query_must_be_ai helper on Input and a new else if branch in input_enter between the existing should_block_cloud_mode_setup_submission guard and the AI/shell branches.

2. Recover from the broken state after Ctrl-C during startup

After Ctrl-C during cloud agent startup the model transitions to Status::Cancelled (and the same broken state applies for Failed / NeedsGithubAuth pre-first-exchange). Re-entering the conversation by clicking the parent terminal’s blocklist entry block left the view in a half-broken layout: the cloud-mode v2 composing input only renders for Status::Composing, so the regular block list + input chrome takes over against a deferred terminal session that has nothing to run.

The fix adds AmbientAgentViewModel::reset_to_composing_after_terminal_state which resets the run back to Composing (clearing task_id, conversation_id, the queued-prompt + harness-started flags, and request) while preserving the user's environment and harness selections. The AmbientAgentEntryBlockAction::OpenAmbientAgent handler calls it before pushing the cloud-mode terminal view back onto the pane stack, so the user lands on a usable composer ready to dispatch a fresh run.

Testing

• cargo fmt -- --check and cargo clippy -p warp --all-targets --tests -- -D warnings both pass cleanly.
• Workspace-wide cargo clippy --workspace --exclude warp_completer --all-targets --tests -- -D warnings could not be run end-to-end in this sandbox because libclang is not installed; the warp package's clippy check passed cleanly which covers all changed files.
• Manual verification will need to confirm:
  • In V1 cloud-mode composing, switching the input to shell mode and pressing Enter shows the new error toast and does not execute anything.
  • Cancelling a cloud agent during startup, returning to the parent terminal, and clicking the blocklist entry block lands the user back on the cloud-mode composer with the previously selected environment and harness still in place.

Server API dependencies

This change does not depend on any server API changes.

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

Changelog Entries for Stable

CHANGELOG-BUG-FIX: Cloud Mode: warn when the first query in a cloud agent run is a shell command, and recover the composer when re-entering a cancelled cloud conversation.

Conversation: https://staging.warp.dev/conversation/c07c27bf-dc85-46a7-ab48-76959ba08fea
Run: https://oz.staging.warp.dev/runs/019ddb0d-c830-790a-b6f7-f544fad95e94

This PR was generated with Oz.

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