feat(claw): a message into a live turn steers it

The resident dispatch's turn now runs under a steer select: the
messages route, after its ingest, signals a per-key interrupt registry,
the drop lands at the turn's current await (an in-flight shell command
dies with it), the dangling calls close, and the dispatch loops on the
same lease — the steered message runs as the next round, same session,
same stream. The interrupted turn closes on the stream with turn_done
carrying outcome "steered", and the shim's whole and streamed
answers both wait through steered end markers for the round that
actually replies.

The messages route answers 202 the moment the message is accepted; the
drain pass runs detached, so a turn's minutes never hold the request
open. The web composer leans on that: it never closes for a running
turn, the placeholder and the send button say that sending steers, a
steered outcome gets its own tone, and the sent-row echo dedup pops a
pending list instead of comparing the last item — a steered chain's
extra end marker can no longer double the row.

web/claw/app/components/ChatPanel.vue

@@ -1,9 +1,12 @@
 <script setup lang="ts">
 // The transcript: sent lines and streamed turns, the turn in flight at
 // the bottom. The claw owns the conversation — this renders what the
-// event stream delivered, nothing more. The header names the session
-// and hides the dispatch internals behind an info modal; the composer
-// chips mirror live claw state; the backend chip jumps to settings.
+// event stream delivered, nothing more. The composer never closes for
+// a running turn: sending while one streams steers it — the claw cuts
+// the turn and answers the message instead (rhema-code's shape). The
+// header names the session and hides the dispatch internals behind an
+// info modal; the composer chips mirror live claw state; the backend
+// chip jumps to settings.
 import {
   PASTE_INLINE_LINES,
   chipLabel,
@@ -82,7 +85,9 @@ watch(
 function submit(): void {
   const text = draft.value.trim()
   // The draft stays the gate: the claw 422s an empty text even with
-  // images aboard.
+  // images aboard. `busy` is only this send's POST in flight (the claw
+  // answers 202 at once) — a running turn never blocks the composer,
+  // because a send into one steers it.
   if (!text || !props.canSend || props.busy) return
   emit('send', { text: embedPastes(text, pastes.value), images: stagedImages.value })
   stageGeneration++
@@ -391,7 +396,7 @@ function streamTone(status: StreamStatus): 'ok' | 'warn' | 'error' {
             <div
               v-if="item.turn.outcome"
               class="outcome mono"
-              :class="{ failed: item.turn.outcome === 'failed' }"
+              :class="{ failed: item.turn.outcome === 'failed', steered: item.turn.outcome === 'steered' }"
             >
               {{ item.turn.outcome }}
             </div>
@@ -465,13 +470,24 @@ function streamTone(status: StreamStatus): 'ok' | 'warn' | 'error' {
           ref="prompt"
           v-model="draft"
           rows="1"
-          :placeholder="canSend ? `Message ${agentName}…` : 'only interactive:* sessions accept messages'"
+          :placeholder="
+            canSend
+              ? live
+                ? `Message ${agentName}… sending steers the running turn`
+                : `Message ${agentName}…`
+              : 'only interactive:* sessions accept messages'
+          "
           :disabled="!canSend"
           @keydown="onPromptKeydown"
           @paste="onPaste"
           @input="resizePrompt"
         />
-        <button class="primary send" :disabled="!canSend || busy || draft.trim() === ''" title="send" @click="submit">
+        <button
+          class="primary send"
+          :disabled="!canSend || busy || draft.trim() === ''"
+          :title="live ? 'send — interrupts the running turn' : 'send'"
+          @click="submit"
+        >
           ↑
         </button>
         <input
@@ -632,6 +648,12 @@ function streamTone(status: StreamStatus): 'ok' | 'warn' | 'error' {
   color: var(--error);
 }
 
+/* A steered turn: cut short by the user's next message — not a
+   failure, the reply that replaced it streams right below. */
+.outcome.steered {
+  color: var(--accent-text);
+}
+
 /* A consent card: the agent asking its human something — distinct
    from a tool row, toned by its resolution. */
 .consent-card {