feat(simulation): add EconEvent stub and import currency zones from TOML

Add D-180 EconEvent struct (target, effect, duration, visibility enums)
with no-op handler to satisfy #809 spec. Import MARK_PRIMARY and MIXED
currency zone assignments from wiki/economics/currency_zones.toml (D-172).
All four D-179 stability tests now pass.

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

tooling/econ-sim/src/agents.rs

@@ -18,6 +18,61 @@
 
 use std::collections::HashMap;
 
+// ---------------------------------------------------------------------------
+// EconEvent — D-180 event port stub (#809)
+// ---------------------------------------------------------------------------
+
+/// Scope of nodes affected by an EconEvent.
+#[derive(Debug, Clone)]
+#[allow(dead_code)]
+pub enum EventTarget {
+    Node(String),
+    NodeSet(Vec<String>),
+    Corridor(String),
+    TradeRoute { from: String, to: String },
+    Currency(String),
+    Commodity(String),
+}
+
+/// Economic effect applied at the target.
+#[derive(Debug, Clone)]
+#[allow(dead_code)]
+pub enum EventEffect {
+    ProductivityMultiplier(f64),
+    CapacityMultiplier(f64),
+    DemandShock(f64),
+    ExchangeShock(f64),
+}
+
+/// Who can observe this event.
+#[derive(Debug, Clone)]
+#[allow(dead_code)]
+pub enum EventVisibility {
+    Global,
+    Proximate(u32),           // hops
+    Disclosed(Vec<String>),   // specific node IDs
+    Hidden,
+}
+
+/// Economic event for injection into the simulation (D-180).
+///
+/// No-op handler until the IPC bridge is in place.
+#[derive(Debug, Clone)]
+#[allow(dead_code)]
+pub struct EconEvent {
+    pub target: EventTarget,
+    pub effect: EventEffect,
+    /// Duration in simulation ticks. 0 = instantaneous.
+    pub duration: u32,
+    pub visibility: EventVisibility,
+}
+
+/// No-op event handler. Called from the tick loop once D-180 IPC is wired.
+#[allow(dead_code)]
+pub fn handle_event(_event: &EconEvent) {
+    // No-op: event port not yet connected (D-180).
+}
+
 // ---------------------------------------------------------------------------
 // Archetype enum
 // ---------------------------------------------------------------------------