Add InfoCommand as one fully-wired real example in bambulab.v1

The rest of proto/bambulab/ was pure boilerplate/comments with nothing
concrete to copy from. This one message (sequence_id + command, matching
Bambu's real get_version request) is wired all the way through: real
proto, real generated Rust struct, lib.rs actually include!'d instead of
commented out. continuum-proxy's bambu_protocol_demo example serializes it
and diffs the output against Bambu's actual wire JSON byte for byte.

Verified with cargo build (this crate) and cargo run --example
bambu_protocol_demo (continuum-proxy) - output matches exactly.

proto/bambulab/v1/request.proto

@@ -2,12 +2,22 @@ syntax = "proto3";
 
 package bambulab.v1;
 
-// import "bambulab/common.proto"; once common.proto has a shared message
-// worth embedding (composition, not inheritance — see that file).
+// One real, fully-wired example — copy this shape for every other command
+// (pushing/pushall, print control, etc.). sequence_id is `string`, not
+// int64: Bambu sends it as a JSON string ("0"), and this crosses the wire
+// as JSON over MQTT, not binary protobuf — the Rust type needs to match
+// what serde_json actually produces, not what "feels more correct" for a
+// counter.
+message InfoCommand {
+  string sequence_id = 1;
+  string command = 2;
+}
 
-// Your command messages go here, e.g.:
+// Add your next message here, e.g.:
 //
-// message InfoCommand {
+// message PushingCommand {
 //   string sequence_id = 1;
 //   string command = 2;
+//   int32 version = 3;
+//   int32 push_target = 4;
 // }