proto: keep cursor ids as strings in JS

A Windows peer before 1.5.0 names a cursor by its handle, sign-extended
above 2^53 when its top bit is set. The web client decodes u64 fields
into JS numbers, and ts-proto throws on a value a number cannot hold,
so each such cursor_data or cursor_id was dropped whole and the web
cursor stayed on the shape before. [jstype = JS_STRING] makes ts-proto
generate these two fields as strings; the wire format, the Rust code
generated and every other client are unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EZ49AbZJYfm8NTp5yDPMab

libs/base/protos/message.proto

@@ -310,7 +310,9 @@ message KeyEvent {
 }
 
 message CursorData {
-  uint64 id = 1;
+  // A string in JS: a Windows peer before 1.5.0 sends its cursor handle, sign-extended above
+  // 2^53 when its top bit is set, which a JS number cannot hold.
+  uint64 id = 1 [jstype = JS_STRING];
   sint32 hotx = 2;
   sint32 hoty = 3;
   int32 width = 4;
@@ -1008,7 +1010,7 @@ message Message {
     AudioFrame audio_frame = 11;
     CursorData cursor_data = 12;
     CursorPosition cursor_position = 13;
-    uint64 cursor_id = 14;
+    uint64 cursor_id = 14 [jstype = JS_STRING]; // as CursorData.id
     KeyEvent key_event = 15;
     Clipboard clipboard = 16;
     FileAction file_action = 17;