replace send_file_dm with open_dm resolver (per review)

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

@@ -93,16 +93,10 @@ struct SendFileArgs {
 }
 
 #[derive(Debug, Deserialize, JsonSchema)]
-struct SendFileDmArgs {
-    /// Matrix user id of the recipient (`@user:server`). DM room is
+struct OpenDmArgs {
+    /// Matrix user id (`@user:server`) to open a DM with. The DM room is
     /// created if one doesn't already exist.
     user_id: String,
-    /// Absolute path to a local file readable by the agent. MIME type is
-    /// inferred from the extension. 50 MiB cap.
-    path: String,
-    /// Optional caption, sent as a follow-up text message in the DM.
-    #[serde(default)]
-    caption: Option<String>,
 }
 
 #[derive(Debug, Deserialize, JsonSchema)]
@@ -240,19 +234,14 @@ impl MatrixBridge {
         )
     }
 
-    #[tool(
-        description = "Open (or reuse) a DM with `user_id` (@user:server) and upload \
-            a local file as an attachment. `path` is an absolute local file path (MIME \
-            inferred, 50 MiB cap); optional `caption` is sent as a follow-up message. \
-            If the DM room already exists with unread messages, the send is rejected \
-            — read_room then mark_read first."
-    )]
-    async fn send_file_dm(&self, Parameters(args): Parameters<SendFileDmArgs>) -> String {
+    #[tool(description = "Resolve (find-or-create) the DM room with `user_id` \
+            (@user:server) and return its room id, without sending anything. Use the \
+            returned room id with the room-based tools (`send_file`, `send_message`, \
+            …) to deliver into the DM — there is no per-tool DM variant.")]
+    async fn open_dm(&self, Parameters(args): Parameters<OpenDmArgs>) -> String {
         render(
-            round_trip(DaemonRequest::SendFileDm {
+            round_trip(DaemonRequest::OpenDm {
                 user_id: args.user_id,
-                path: args.path,
-                caption: args.caption,
             })
             .await,
         )