cancel_thread: new mcp tool — unify reminder + question cancel on both surfaces

hive-c0re/src/operator_questions.rs

@@ -196,6 +196,54 @@ impl OperatorQuestions {
         Ok((question, asker, target))
     }
 
+    /// Cancel a pending question on behalf of `canceller`. Returns
+    /// `(question, asker, target)` so the caller can fire the usual
+    /// `QuestionAnswered` event to the asker with a `[cancelled by
+    /// <canceller>]` sentinel.
+    ///
+    /// Auth: the canceller must be one of:
+    /// - the original asker (an agent withdrawing their own ask),
+    /// - the operator (already covered by the existing `answer` path
+    ///   but allowed here too for symmetry / dashboard cancel),
+    /// - the manager (privileged hive-wide cleanup).
+    ///
+    /// Not the target — that's covered by `answer` (responding with
+    /// an actual reply, sentinel or otherwise).
+    pub fn cancel(
+        &self,
+        id: i64,
+        canceller: &str,
+    ) -> Result<(String, String, Option<String>)> {
+        let conn = self.conn.lock().unwrap();
+        let row: Option<(String, String, Option<String>, Option<i64>)> = conn
+            .query_row(
+                "SELECT question, asker, target, answered_at FROM operator_questions WHERE id = ?1",
+                params![id],
+                |row| Ok((row.get(0)?, row.get(1)?, row.get(2)?, row.get(3)?)),
+            )
+            .optional()?;
+        let Some((question, asker, target, answered_at)) = row else {
+            bail!("question {id} not found");
+        };
+        if answered_at.is_some() {
+            bail!("question {id} already answered/cancelled");
+        }
+        let authorised = canceller == asker
+            || canceller == hive_sh4re::OPERATOR_RECIPIENT
+            || canceller == hive_sh4re::MANAGER_AGENT;
+        if !authorised {
+            bail!(
+                "question {id}: '{canceller}' not allowed to cancel (asker = '{asker}')"
+            );
+        }
+        let sentinel = format!("[cancelled by {canceller}]");
+        conn.execute(
+            "UPDATE operator_questions SET answer = ?1, answered_at = ?2 WHERE id = ?3",
+            params![sentinel, now_unix(), id],
+        )?;
+        Ok((question, asker, target))
+    }
+
     #[allow(dead_code)]
     pub fn get(&self, id: i64) -> Result<Option<OpQuestion>> {
         let conn = self.conn.lock().unwrap();