fix(simulation): address PR #125 review — tick truncation, ordering, perf, protocol test

- Widen EventPort tick methods from u32 to u64 (prevents overflow)
- Add is_identity() guard on hot-path String allocation in modifiers
- Replace Vec::remove(0) with VecDeque::pop_front() in price history
- Add .after(tick_economy_simulation) ordering for debug commands
- Fix stale PROTOCOL_VERSION assertion (20 → 21) in serialization test
- Add D-181 Phase 2 visibility scope comment on serve_econ_state_query
- Eliminate double lookup in rebuild_signals via single-pass extraction
- Track economy seed TODO with backlog ticket reference

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

tooling/econ-sim/src/main.rs

@@ -376,7 +376,7 @@ fn run_shock_response_test(
     // Schedule: inject 90% capacity disruption at tick WARMUP_TICKS
     let mut port = events::EventPort::new();
     port.push_at(
-        WARMUP_TICKS,
+        WARMUP_TICKS as u64,
         events::EconEvent {
             target: events::EconEventTarget::Node(shock_node.clone()),
             effect: events::EconEventEffect::CapacityMultiplier(0.1),