feat(desktop): steer the live run from the composer

The desktop app could only queue while busy — `/steer` was in the palette
but had no first-class affordance, so the "nudge the agent mid-turn without
interrupting" lane was effectively unreachable.

Add a steer action to the composer: while busy with a text-only draft, a
steering-wheel button (and Cmd/Ctrl+Enter) injects the text into the live
turn via the `session.steer` RPC — the gateway folds it into the next tool
result so the model reads it on its next iteration. Plain Enter still queues.

steerPrompt returns false when the gateway has no live tool window (or the
RPC errors), and the composer re-queues the words so nothing is lost — the
same safety net as a plain queue.

apps/desktop/src/app/chat/composer/controls.tsx

@@ -3,7 +3,7 @@ import { Codicon } from '@/components/ui/codicon'
 import { Tip } from '@/components/ui/tooltip'
 import { useI18n } from '@/i18n'
 import { triggerHaptic } from '@/lib/haptics'
-import { AudioLines, Layers3, Loader2, Square } from '@/lib/icons'
+import { AudioLines, Layers3, Loader2, Square, SteeringWheel } from '@/lib/icons'
 import { cn } from '@/lib/utils'
 
 import type { ConversationStatus } from './hooks/use-voice-conversation'
@@ -38,16 +38,19 @@ interface ConversationProps {
 export function ComposerControls({
   busy,
   busyAction,
+  canSteer,
   canSubmit,
   conversation,
   disabled,
   hasComposerPayload,
   state,
   voiceStatus,
-  onDictate
+  onDictate,
+  onSteer
 }: {
   busy: boolean
   busyAction: 'queue' | 'stop'
+  canSteer: boolean
   canSubmit: boolean
   conversation: ConversationProps
   disabled: boolean
@@ -55,6 +58,7 @@ export function ComposerControls({
   state: ChatBarState
   voiceStatus: VoiceStatus
   onDictate: () => void
+  onSteer: () => void
 }) {
   const { t } = useI18n()
   const c = t.composer
@@ -68,6 +72,21 @@ export function ComposerControls({
   return (
     <div className="ml-auto flex shrink-0 items-center gap-(--composer-control-gap)">
       <DictationButton disabled={disabled} onToggle={onDictate} state={state.voice} status={voiceStatus} />
+      {canSteer && (
+        <Tip label={c.steer}>
+          <Button
+            aria-label={c.steer}
+            className={GHOST_ICON_BTN}
+            disabled={disabled}
+            onClick={onSteer}
+            size="icon"
+            type="button"
+            variant="ghost"
+          >
+            <SteeringWheel size={16} />
+          </Button>
+        </Tip>
+      )}
       {showVoicePrimary ? (
         <Tip label={c.startVoice}>
           <Button

apps/desktop/src/app/chat/composer/index.tsx

@@ -123,6 +123,7 @@ export function ChatBar({
   onPickFolders,
   onPickImages,
   onRemoveAttachment,
+  onSteer,
   onSubmit,
   onTranscribeAudio
 }: ChatBarProps) {
@@ -169,6 +170,10 @@ export function ChatBar({
   const canSubmit = busy || hasComposerPayload
   const editingQueuedPrompt = queueEdit ? (queuedPrompts.find(entry => entry.id === queueEdit.entryId) ?? null) : null
   const busyAction = busy && hasComposerPayload ? 'queue' : 'stop'
+  // Steer only makes sense mid-turn, text-only (the gateway can't carry images
+  // into a tool result) and never for a slash command (those execute inline).
+  const canSteer =
+    busy && !!onSteer && attachments.length === 0 && draft.trim().length > 0 && !SLASH_COMMAND_RE.test(draft.trim())
   const showHelpHint = draft === '?'
 
   const { t } = useI18n()
@@ -792,6 +797,15 @@ export function ChatBar({
       return
     }
 
+    // Cmd/Ctrl+Enter steers the draft into the live run (nudge, no interrupt);
+    // plain Enter still queues while busy.
+    if (event.key === 'Enter' && (event.metaKey || event.ctrlKey) && !event.shiftKey && canSteer) {
+      event.preventDefault()
+      steerDraft()
+
+      return
+    }
+
     if (event.key === 'Enter' && !event.shiftKey) {
       event.preventDefault()
 
@@ -1070,6 +1084,26 @@ export function ChatBar({
     return true
   }, [activeQueueSessionKey, attachments, clearDraft, draft])
 
+  // Steer the live turn (nudge without interrupting). Clears the draft up front
+  // for snappy feedback; if the gateway rejects (no live tool window) the words
+  // are re-queued so nothing is lost — same safety net as a plain queue.
+  const steerDraft = useCallback(() => {
+    if (!onSteer || !canSteer) {
+      return
+    }
+
+    const text = draftRef.current.trim()
+
+    triggerHaptic('submit')
+    clearDraft()
+
+    void Promise.resolve(onSteer(text)).then(accepted => {
+      if (!accepted && activeQueueSessionKey) {
+        enqueueQueuedPrompt(activeQueueSessionKey, { text, attachments: [] })
+      }
+    })
+  }, [activeQueueSessionKey, canSteer, clearDraft, onSteer])
+
   // All queue drain paths share one lock + send-then-remove sequence.
   // `pickEntry` lets each caller choose head, by-id, or skip-edited.
   const runDrain = useCallback(
@@ -1305,6 +1339,7 @@ export function ChatBar({
     <ComposerControls
       busy={busy}
       busyAction={busyAction}
+      canSteer={canSteer}
       canSubmit={canSubmit}
       conversation={{
         active: voiceConversationActive,
@@ -1322,6 +1357,7 @@ export function ChatBar({
       disabled={disabled}
       hasComposerPayload={hasComposerPayload}
       onDictate={dictate}
+      onSteer={steerDraft}
       state={state}
       voiceStatus={voiceStatus}
     />

apps/desktop/src/app/chat/composer/types.ts

@@ -47,6 +47,7 @@ export interface ChatBarProps {
   onPickFolders?: () => void
   onPickImages?: () => void
   onRemoveAttachment?: (id: string) => void
+  onSteer?: (text: string) => Promise<boolean> | boolean
   onSubmit: (
     value: string,
     options?: { attachments?: ComposerAttachment[]; fromQueue?: boolean }

apps/desktop/src/app/chat/index.tsx

@@ -72,6 +72,7 @@ interface ChatViewProps extends Omit<React.ComponentProps<'div'>, 'onSubmit'> {
   onPickFolders: () => void
   onPickImages: () => void
   onRemoveAttachment: (id: string) => void
+  onSteer: (text: string) => Promise<boolean> | boolean
   onSubmit: (
     text: string,
     options?: { attachments?: ComposerAttachment[]; fromQueue?: boolean }
@@ -164,6 +165,7 @@ export function ChatView({
   onPickFolders,
   onPickImages,
   onRemoveAttachment,
+  onSteer,
   onSubmit,
   onThreadMessagesChange,
   onEdit,
@@ -370,6 +372,7 @@ export function ChatView({
                 onPickFolders={onPickFolders}
                 onPickImages={onPickImages}
                 onRemoveAttachment={onRemoveAttachment}
+                onSteer={onSteer}
                 onSubmit={onSubmit}
                 onTranscribeAudio={onTranscribeAudio}
                 queueSessionKey={selectedSessionId || activeSessionId}