Wire classifySubmit through the runner host and empty Enter cancel

The busy-path fix was dropped at mountRunnerHost, so typecheck failed on
classifySubmit. Empty Enter also never reached exclusive hooks, so armed
/feedback cancel was dead code until the shell lets blank lines through.

Author: TheGreatAxios

src/tui/prompt-features.test.ts

@@ -234,6 +234,20 @@ describe("image attachments", () => {
       expect(texts).toEqual([""])
     })
   })
+
+  test("empty Enter still reaches exclusive host for multi-turn cancel", async () => {
+    await withShell(async (shell) => {
+      const submitted: string[] = []
+      setShellBridgeHooks(shell, {
+        onSubmit: (text) => submitted.push(text),
+        onInterrupt: () => {},
+        exclusive: true,
+      })
+      shell.prompt.value = "   "
+      submitPrompt(shell)
+      expect(submitted).toEqual(["   "])
+    })
+  })
 })
 
 /**

src/tui/runner-host.ts

@@ -56,6 +56,14 @@ export type RunnerHostDeps = {
     text: string,
     attachments?: readonly PendingImageAttachment[],
   ) => void
+  /**
+   * Classify a submit without side effects so slash commands and multi-turn
+   * /feedback never mark the session busy or enter the mid-run queue.
+   */
+  readonly classifySubmit?: (
+    text: string,
+    attachments?: readonly PendingImageAttachment[],
+  ) => "agent" | "local" | "empty"
   readonly interrupt: () => void
   readonly deliver?: (
     text: string,
@@ -249,6 +257,9 @@ export async function mountRunnerHost(deps: RunnerHostDeps): Promise<RunnerHost>
     eventEmitter: deps.eventEmitter,
     send: deps.send,
     interrupt: deps.interrupt,
+    ...(deps.classifySubmit !== undefined
+      ? { classifySubmit: deps.classifySubmit }
+      : {}),
     ...(deps.deliver !== undefined ? { deliver: deps.deliver } : {}),
     ...(deps.onConnectProvider !== undefined
       ? { onConnectProvider: deps.onConnectProvider }

src/tui/shell.ts

@@ -3138,7 +3138,15 @@ export function submitPrompt(
   const text = shell.prompt.value
   const t = text.trim()
   const attachments = shell.pendingAttachments
-  if (t.length === 0 && attachments.length === 0) return
+  if (t.length === 0 && attachments.length === 0) {
+    // Empty Enter still reaches the exclusive host so multi-turn /feedback
+    // can cancel; non-exclusive shells have nothing to do with a blank line.
+    const hooks = getShellBridgeHooks(shell)
+    if (hooks?.exclusive) {
+      hooks.onSubmit(text, "immediate", attachments)
+    }
+    return
+  }
   if (kind === "reinject" && shell.session.run !== "busy") return
 
   // Shell/REPL muscle memory: a bare `exit` or `quit` quits rather than being