feat(#1685): surface attachments in read_room + add download_file

hive-matrix-mcp/src/bin/mcp.rs

@@ -138,6 +138,19 @@ struct ReadRoomArgs {
     limit: Option<usize>,
 }
 
+#[derive(Debug, Deserialize, JsonSchema)]
+struct DownloadFileArgs {
+    /// Matrix room id (`!abc:server`) or canonical alias (`#name:server`).
+    room: String,
+    /// Event id of the attachment message (from `read_room`, where media
+    /// events show a `[file: …]` / `[image: …]` marker).
+    event_id: String,
+    /// Optional absolute destination path. Omit to write a temp file
+    /// named after the attachment; the returned `path` is where to read it.
+    #[serde(default)]
+    dest_path: Option<String>,
+}
+
 #[derive(Debug, Deserialize, JsonSchema)]
 struct ListInvitesArgs {}
 
@@ -380,6 +393,24 @@ impl MatrixBridge {
             .await,
         )
     }
+
+    #[tool(
+        description = "Download a media attachment from a matrix message to a local \
+            file and return its path. `room` is a room id/alias; `event_id` is the \
+            attachment message (read_room shows media as `[file: …]`/`[image: …]`); \
+            optional `dest_path` overrides the temp destination. The read-side \
+            counterpart of send_file."
+    )]
+    async fn download_file(&self, Parameters(args): Parameters<DownloadFileArgs>) -> String {
+        render(
+            round_trip(DaemonRequest::DownloadFile {
+                room: args.room,
+                event_id: args.event_id,
+                dest_path: args.dest_path,
+            })
+            .await,
+        )
+    }
 }
 
 #[tool_handler(instructions = "Matrix client for an agent on a hyperhive swarm. Use \