test(web): cover empty-draft queue flush with a keyless replay scenario

Also pin the queue-item-not-found convergence arm through the hub and
document the repeated-trigger contract on steerQueue.

apps/web/tests/snapshots/steer-all/mid-steer.expected.md

@@ -0,0 +1,36 @@
+- banner:
+  - navigation "Session hierarchy":
+    - button "Use the ask_user_question tool to" [disabled]
+  - tablist:
+    - tab "Chat" [selected]
+    - tab "Trajectory"
+- text: Use the ask_user_question tool to ask me exactly one question with id "checkpoint", question "Ready to continue?", header "Checkpoint", and options labeled "Yes" and "No". After I answer, reply with one short sentence acknowledging my answer and stop. {{clock}}
+- button "Copy":
+  - img
+- button "Branch into a new conversation" [disabled]:
+  - img
+- text: Available only on the last message of a completed turn
+- button "Context injection @deepseek-ai/dsh-system-prompt":
+  - img
+  - img
+  - text: Context injection @deepseek-ai/dsh-system-prompt
+- text: Running
+- button "Think":
+  - img
+  - img
+  - text: Think
+- status: Deep diving...
+- text: "Interjection Interjection: include the word BANANA in your final reply."
+- button "Copy":
+  - img
+- text: "Interjection Interjection: include the word ORANGE in your final reply."
+- button "Copy":
+  - img
+- textbox "Message the agent"
+- button "Commands":
+  - img
+- 'button "Access mode, current: Workspace Write"': Workspace Write
+- button "Select model, current DeepSeek-V4-Flash":
+  - text: DeepSeek-V4-Flash
+  - img
+- button "Stop generating"