feat: support idempotent clarification dismiss over stdio (A6)

src-tauri/crates/altai-cli/src/serve/mod.rs

@@ -440,12 +440,18 @@ pub async fn run(workspace: WorkspacePaths) -> Result<(), String> {
                         .and_then(|value| value.as_object().cloned())
                         .unwrap_or_default();
                     let chat_id = params.get("chat_id").and_then(Value::as_str).unwrap_or("");
+                    let action = params.get("action").and_then(Value::as_str).unwrap_or("reply");
                     let text = params.get("text").and_then(Value::as_str).unwrap_or("");
-                    if chat_id.trim().is_empty() || chat_id.len() > 256 || text.trim().is_empty() || text.len() > 16_384 {
+                    if chat_id.trim().is_empty() || chat_id.len() > 256 || !matches!(action, "reply" | "dismiss") || (action == "reply" && (text.trim().is_empty() || text.len() > 16_384)) {
                         respond(&writer, id, None, Some(error_value(-32602, "invalid_clarification_response"))).await?;
                         continue;
                     }
-                    match host.deliver_clarification_reply(chat_id, text.to_string()).await {
+                    let result = if action == "dismiss" {
+                        host.dismiss_clarification(chat_id).await
+                    } else {
+                        host.deliver_clarification_reply(chat_id, text.to_string()).await
+                    };
+                    match result {
                         Ok(()) => respond(&writer, id, Some(json!({"accepted": true})), None).await?,
                         Err(error) => respond(&writer, id, None, Some(error_value(-32002, &error))).await?,
                     }

src-tauri/crates/altai-cli/src/stdio_host.rs

@@ -86,6 +86,21 @@ impl StdioHost {
         }
     }
 
+    /// Dismiss a live clarification exactly once.
+    pub async fn dismiss_clarification(&self, chat_id: &str) -> Result<(), String> {
+        let workspace_root = self.workspace.root.to_string_lossy().to_string();
+        let services = self.workspace_bundle_inner(&workspace_root).await?;
+        let session_key = isanagent::bus::clarification_session_key("stdio", chat_id, None);
+        if services
+            .clarification_hub
+            .cancel_wait_if_pending(&session_key)
+        {
+            Ok(())
+        } else {
+            Err("clarification_not_pending".to_string())
+        }
+    }
+
     async fn workspace_bundle_inner(
         &self,
         workspace_root: &str,

src-tauri/crates/altai-cli/tests/serve_stdio.rs

@@ -151,8 +151,10 @@ fn clarification_response_rejects_a_non_pending_ticket() {
     assert_eq!(process.next()["id"], 1);
     process.frame(json!({"jsonrpc":"2.0","id":2,"method":"clarification/respond","params":{"chat_id":"chat-test","text":"yes"}}));
     assert_eq!(process.next()["error"]["message"], "clarification_not_pending");
-    process.frame(json!({"jsonrpc":"2.0","id":3,"method":"shutdown"}));
-    assert_eq!(process.next()["id"], 3);
+    process.frame(json!({"jsonrpc":"2.0","id":3,"method":"clarification/respond","params":{"chat_id":"chat-test","action":"dismiss"}}));
+    assert_eq!(process.next()["error"]["message"], "clarification_not_pending");
+    process.frame(json!({"jsonrpc":"2.0","id":4,"method":"shutdown"}));
+    assert_eq!(process.next()["id"], 4);
     let _stderr = process.shutdown();
 }