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>

server/src/simulation/economy.rs

@@ -31,7 +31,7 @@
 //! 6. `production_vs_baseline` — supply ÷ initial baseline supply (Private)
 //! 7. `official_coverage_ratio` — 1 − shadow_intensity (Meta-signal)
 
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, VecDeque};
 
 use bevy_ecs::prelude::*;
 use econ_sim::Simulation;
@@ -61,7 +61,7 @@ pub struct EconSimResource {
     pub sim: Simulation,
     /// Price history for signal 2 (price_trend) computation.
     /// Ring-buffer keyed by (system_id, commodity_id) → last TREND_WINDOW prices.
-    price_history: BTreeMap<(String, String), Vec<f64>>,
+    price_history: BTreeMap<(String, String), VecDeque<f64>>,
     /// Baseline supply from first economy tick for signal 6 (production_vs_baseline).
     baseline_supply: BTreeMap<(String, String), f64>,
 }
@@ -188,15 +188,17 @@ fn rebuild_signals(
 
     // Snapshot current node states into the price_history and baseline_supply maps,
     // then build signals.  We need to separate the borrow from the iteration.
-    let node_snapshots: Vec<(String, Vec<(String, f64, f64)>)> = econ_sim
+    let node_snapshots: Vec<(String, Vec<(String, f64, f64, f64, f64)>)> = econ_sim
         .sim
         .nodes
         .iter()
         .map(|(system_id, node)| {
-            let commodities: Vec<(String, f64, f64)> = node
+            let commodities: Vec<(String, f64, f64, f64, f64)> = node
                 .commodities
                 .iter()
-                .map(|(commodity_id, state)| (commodity_id.clone(), state.price, state.supply))
+                .map(|(commodity_id, state)| {
+                    (commodity_id.clone(), state.price, state.supply, state.stockpile, state.demand)
+                })
                 .collect();
             (system_id.clone(), commodities)
         })
@@ -206,7 +208,7 @@ fn rebuild_signals(
         let shadow_intensity = shadow_intensities.get(system_id).copied().unwrap_or(0.0);
         let corp_count = corp_counts.get(system_id).copied().unwrap_or(0);
 
-        for (commodity_id, price, supply) in commodities {
+        for (commodity_id, price, supply, stockpile, demand) in commodities {
             let key = (system_id.clone(), commodity_id.clone());
 
             // Signal 6 baseline: record first-tick supply
@@ -218,9 +220,9 @@ fn rebuild_signals(
 
             // Signal 2: price trend via ring buffer
             let history = econ_sim.price_history.entry(key.clone()).or_default();
-            history.push(*price);
+            history.push_back(*price);
             if history.len() > TREND_WINDOW {
-                history.remove(0);
+                history.pop_front();
             }
             let price_trend = if history.len() >= 2 {
                 price - history[0]
@@ -229,23 +231,9 @@ fn rebuild_signals(
             };
 
             // Signal 5: stockpile in weeks (7 economy ticks per week approximation)
-            let stockpile = econ_sim
-                .sim
-                .nodes
-                .get(system_id)
-                .and_then(|n| n.commodities.get(commodity_id))
-                .map(|s| s.stockpile)
-                .unwrap_or(0.0);
-            let demand = econ_sim
-                .sim
-                .nodes
-                .get(system_id)
-                .and_then(|n| n.commodities.get(commodity_id))
-                .map(|s| s.demand)
-                .unwrap_or(0.0);
             let weekly_demand = demand * 7.0; // 7 econ ticks ≈ 1 week
             let stockpile_weeks = if weekly_demand > 1e-9 {
-                stockpile / weekly_demand
+                *stockpile / weekly_demand
             } else {
                 0.0
             };
@@ -297,6 +285,11 @@ pub struct EconQueryBuffer {
 /// Runs after `tick_economy_simulation` (signals must be fresh) and before
 /// `compute_observer_snapshot` (which consumes the response).
 /// No-op when `EconStateResource` is absent or no query is pending.
+///
+/// **D-181 visibility (Phase 2):** All 7 signals are sent unfiltered.
+/// Phase 3 will gate signals 3–7 behind the D-181 visibility ladder
+/// (Observable → Semi-private → Private → Meta) based on the player's
+/// information access at the queried node.
 pub fn serve_econ_state_query(
     mut query_buf: ResMut<EconQueryBuffer>,
     econ_state: Option<Res<EconStateResource>>,

server/src/simulation/mod.rs

@@ -168,7 +168,7 @@ impl Plugin for SimulationPlugin {
         app.init_resource::<ticker::TickerPool>();
 
         // Economy simulation (#821, D-031) — loaded once at startup, no-op when DB absent.
-        // Uses seed 0 for now; will be threaded through StartupMessage world seed (#TODO).
+        // Uses seed 0 for now; will be threaded through StartupMessage world seed (#826).
         if let Some((econ_sim, econ_state)) = economy::try_load_economy(0) {
             app.insert_resource(econ_sim).insert_resource(econ_state);
         }