fix(ci): address PR #69 review — stale comments, dead CLI flags

- gen_fixtures.rs: version comments now say PROTOCOL_VERSION instead
  of hardcoded 14, so they stay correct across bumps
- run-ipc-benchmark: remove --iterations flag that was parsed but
  never forwarded to the Rust test (compile-time constant governs)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/tests/gen_fixtures.rs

@@ -290,7 +290,7 @@ fn generate_msgpack_fixtures() {
 
     // === #271 fixtures: named fixtures for cross-language Layer 1 testing ===
 
-    // snapshot_minimal: version=14, tick=0, one Player entity, all optionals absent
+    // snapshot_minimal: version=PROTOCOL_VERSION, tick=0, one Player entity, all optionals absent
     let snapshot_minimal = fixture_snapshot(
         0,
         vec![VisibleEntity {
@@ -310,7 +310,7 @@ fn generate_msgpack_fixtures() {
         &rmp_serde::to_vec_named(&snapshot_minimal).unwrap(),
     );
 
-    // snapshot_full: version=14, tick=42, monologue + dialogue + inventory + POIs + KG dump
+    // snapshot_full: version=PROTOCOL_VERSION, tick=42, monologue + dialogue + inventory + POIs + KG dump
     let snapshot_full = ObserverSnapshot {
         version: PROTOCOL_VERSION,
         tick: 42,