feat(simulation): implement economics integration sprint — #810 #821 #822 #823

Implements the full D-180/D-181 economics pipeline:

**#810 — Event input port (D-180)**
- Add EconEvent struct with Target/Effect/Duration/Visibility variants
- Implement EventPort as typed input queue for external disruptions
- Apply events in simulation step; D-179 Test 3 now uses real shock injection

**#821 — Integrate econ-sim into server tick loop**
- Extract econ-sim as library crate (lib.rs + sim.rs, Cargo.toml [lib] section)
- Add Simulation stateful runner; step() advances one economy tick
- Add EconSimResource, EconStateResource (7 D-181 signals), tick_economy_simulation
- Economy loads once at startup; graceful no-op when systems.db absent
- Server advances economy 1 tick per 10 game ticks (D-031)

**#822 — Expose economy state over IPC bridge**
- Protocol version 20 → 21
- Add EconomySnapshot, EconNodeSnapshot wire types
- Add EconStateQuery PlayerAction variant; response in economy_snapshot field
- Add EconQueryBuffer resource + serve_econ_state_query system

**#823 — Economics debug commands**
- Add InjectEconEvent, SetEconParam, GetEconState to DebugCommandKind
- Add EconDebugEffect, EconParamKind enums
- SetEconParam mutates α/β at runtime (α/β promoted to pub const + Simulation fields)
- ALPHA and BETA constants threaded through step_inner/trade_step signatures

All 1147 unit tests pass; zero warnings.

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

server/src/perception/observer/mod.rs

@@ -394,6 +394,9 @@ pub fn compute_observer_snapshot(
         None
     };
 
+    // Consume pending economy snapshot for this tick (#822).
+    let economy_snapshot = buffer.pending_economy_response.take();
+
     // Consume pending save/load result for this tick (#553).
     let save_result = buffer.pending_save_result.take();
 
@@ -489,6 +492,7 @@ pub fn compute_observer_snapshot(
         debug_response,
         current_ticker,
         settings_response,
+        economy_snapshot,
     });
 }