list room senders in prompt for per-person notes discovery

src/main.rs

@@ -359,6 +359,25 @@ async fn invoke_claude(
     )
     .unwrap();
 
+    // Collect unique non-self senders for per-person note discovery
+    let mut senders: Vec<&OwnedUserId> = history
+        .iter()
+        .filter(|m| !m.is_self)
+        .map(|m| &m.sender)
+        .collect();
+    senders.sort();
+    senders.dedup();
+    if !senders.is_empty() {
+        writeln!(
+            prompt,
+            "\n[people in this room — check ../people/<user_id>/notes.md for each]"
+        )
+        .unwrap();
+        for s in &senders {
+            writeln!(prompt, "  {s}").unwrap();
+        }
+    }
+
     let seen = seen_idx.min(history.len());
     let (old, new) = history.split_at(seen);