Fix gateway bot Claude Code cwd so MCP tools are discovered

In gateway mode the bot's Claude Code CLI was spawned with cwd set to
a nonexistent project subdirectory (gateway_config_dir/project_name).
This meant it couldn't find .mcp.json and had no MCP tools available.

Now the bot uses the gateway config directory as cwd in gateway mode,
where the auto-generated .mcp.json points to the gateway's MCP proxy.

Also fixes cargo fmt formatting.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/chat/transport/matrix/bot/messages.rs

@@ -207,8 +207,10 @@ pub(super) async fn on_room_message(
             && (crate::chat::commands::commands()
                 .iter()
                 .any(|c| c.name == cmd)
-                || ["assign", "start", "delete", "rebuild", "rmtree", "htop", "timer"]
-                    .contains(&cmd.as_str()));
+                || [
+                    "assign", "start", "delete", "rebuild", "rmtree", "htop", "timer",
+                ]
+                .contains(&cmd.as_str()));
 
         if is_known_command {
             // Proxy to the active project server.
@@ -643,12 +645,18 @@ pub(super) async fn handle_message(
     let sent_any_chunk = Arc::new(AtomicBool::new(false));
     let sent_any_chunk_for_callback = Arc::clone(&sent_any_chunk);
 
-    // In gateway mode, run Claude Code in the active project's directory.
-    let project_root_str = ctx
-        .effective_project_root()
-        .await
-        .to_string_lossy()
-        .to_string();
+    // In gateway mode, run Claude Code in the gateway config directory so it
+    // picks up the `.mcp.json` that points to the gateway's MCP proxy endpoint.
+    // The gateway proxies tool calls to the active project automatically.
+    // In standalone mode, use the project root directly.
+    let project_root_str = if ctx.is_gateway() {
+        ctx.project_root.to_string_lossy().to_string()
+    } else {
+        ctx.effective_project_root()
+            .await
+            .to_string_lossy()
+            .to_string()
+    };
     let chat_fut = provider.chat_stream(
         &prompt,
         &project_root_str,