feat: queue follow-ups by default, steer with Ctrl+Enter

[dorlanpabon]

Issue for this PR

Closes #44108

Type of change

• New feature

What does this PR do?

Busy-session follow-ups were always steered (the queue setting was force-migrated to steer). Now Enter follows the follow-up setting (queue by default, runs as next turn when idle) and Ctrl+Enter forces a steer into the running turn. Restores the Queue/Steer setting row, passes delivery to the V2 prompt API, and adds the same Enter/Ctrl+Enter split to the mini-TUI queue and legacy TUI prompt.

How did you verify your code works?

• bun typecheck in packages/app, packages/opencode, packages/tui: pass
• bun test prompt-input/submit.test.ts (with --conditions=solid --preload ./happydom.ts): 11/11 pass, incl. 3 new delivery tests
• bun test runtime.queue.test.ts: 16/16 pass

Screenshots / recordings

UI-only hint text change (Enter queue / Ctrl+Enter steer); no layout change, skipping recording. Happy to add one on request.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

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[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Related PRs Found

#44117 - fix(app): restore queued follow-up (Queue/Steer) setting in web UI

• This appears to be directly related, as PR feat: queue follow-ups by default, steer with Ctrl+Enter #47004 mentions "Restores the Queue/Steer setting row" and references issue [FEATURE]: Web UI has no way to queue follow-up messages — steer-only since queue setting was removed #44108, which may be connected to this fix.

#44869 - feat(app): queue follow-ups for new users

• Related to the queue follow-ups feature, though this is specifically for new users while feat: queue follow-ups by default, steer with Ctrl+Enter #47004 is the general queue-by-default implementation.

Note: PR #47004 (the current PR) appears in the search results. The other results (#43073, #41344) don't appear to be duplicates of this PR's core functionality.

[dorlanpabon]

Note for reviewers: #44117 (open) restores the Queue/Steer setting row — this PR overlaps on those 3 settings files and goes further: it wires delivery through to the V2 prompt API (Enter follows the setting, queue by default; Ctrl+Enter forces a steer) plus the same Enter/Ctrl+Enter split in the mini-TUI and legacy TUI. Happy to rebase on top of #44117 if it merges first.

[dorlanpabon]

Suggested labels for triage (I do not have label permissions): enhancement, web, tui. Base branch: dev.

[dorlanpabon]

Superseded by #47031 against v2: the v2 branch already ships the full queue/steer machinery (FollowUpBehavior setting, ComposerQueue, inbox APIs), so only the queue-by-default flip was ported. Keeping this dev-based PR for reference.