feat: add Steer and Queue follow-up modes alongside Chat/Plan

[Fanzzzd]

Right now T3 Code appears to only model default and plan interaction modes. I’d like to request support for Steer and Queue style follow-up behavior while a run is already active.

Why

When the agent is already working, users often want two different behaviors:

• Steer: inject immediate guidance into the active run
• Queue: save the follow-up so it runs after the current work settles

This is a meaningful UX distinction and avoids forcing users into interrupt-or-wait behavior only.

Settings ask

It would be even better if this can be configured in Settings, for example:

• default follow-up behavior while a run is active
• whether the composer shows Steer / Queue explicitly
• an optional shortcut for sending the non-default behavior once

Suggested acceptance criteria

• The composer exposes both follow-up modes when a run is active.
• The selected mode is visible and predictable.
• Users can configure the default active-run follow-up behavior in Settings.
• Queued follow-ups survive reconnects/reloads.
• Steering a run does not silently discard already queued follow-ups.

Relevant code context

• packages/contracts/src/orchestration.ts
• apps/web/src/components/ChatView.tsx
• apps/server/src/orchestration/Layers/ProviderCommandReactor.ts

Reference implementation ideas

• CodexMonitor already exposes configurable follow-up behavior with Queue vs Steer while a run is active.

[MatejSkarka]

+1 for this, for sure for "Steer". This is very usefull function in Codex.

[CanRau]

@MatejSkarka You can already steer by just adding messages, so basically only queueing is missing with clear UI, from my understanding

[juliusmarminge]

yes it's all steer now. we'll add queinig!

[aashishsingla567]

+1 Queue is very important

[FleetAdmiralJakob]

This is a big one and super important for me