feat(@projects/@magic-civilization): 🛤️ Rail-1 Phase-0 — project Golden Age state to the HUD

ResourceView gains golden_age_active + golden_age_turns, projected from the
PlayerState GA fields. These are the top_bar.gd:162/169 entity reads now
available via view_json (HUD badge driven by Rust, not the Player entity).
Omitted from the wire when inactive. Per-city culture_stored (city_screen.gd:287)
is DEFERRED: it has no bench CityState backing (culture is a player-level pool in
the reduced model) — a Phase-1 SOT-flip widening, not fabricated here.

Additive (serde defaults). mc-player-api 140/0 incl. a GA round-trip/omission test.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/simulator/crates/mc-player-api/src/projection.rs

@@ -162,6 +162,10 @@ fn project_resources(player: &mc_state::game_state::PlayerState) -> ResourceView
         // p3-26 B1: surface the happiness pool now computed by the turn's
         // happiness_phase (was hardcoded 0 before the phase existed).
         happiness_pool: player.happiness,
+        // Rail-1: surface the Golden Age state the HUD badge reads
+        // (top_bar.gd:162/169) so it comes from view_json, not the entity.
+        golden_age_active: player.golden_age_active,
+        golden_age_turns: player.golden_age_turns.max(0) as u32,
         stockpile,
     }
 }

src/simulator/crates/mc-player-api/src/view.rs

@@ -36,10 +36,21 @@ pub struct ResourceView {
     pub culture_per_turn: i32,
     /// Global happiness pool (positive = surplus).
     pub happiness_pool: i32,
+    /// Whether the empire is in a Golden Age (drives the HUD badge).
+    #[serde(default, skip_serializing_if = "core::ops::Not::not")]
+    pub golden_age_active: bool,
+    /// Golden-age turns remaining (`0` when not active).
+    #[serde(default, skip_serializing_if = "crate::view::is_zero_u32")]
+    pub golden_age_turns: u32,
     /// Strategic-resource stockpile (resource_id → amount).
     pub stockpile: std::collections::BTreeMap<String, i32>,
 }
 
+/// serde helper: skip `u32` fields that are zero (wire economy).
+pub(crate) fn is_zero_u32(v: &u32) -> bool {
+    *v == 0
+}
+
 /// Research / tech tab state.
 #[derive(Debug, Clone, Default, PartialEq, Serialize, Deserialize)]
 pub struct ResearchView {
@@ -477,6 +488,20 @@ mod tests {
         assert!(!json.contains("posture"), "resting posture must be omitted: {json}");
     }
 
+    #[test]
+    fn resource_view_golden_age_round_trips_and_omits_when_inactive() {
+        let mut r = ResourceView::default();
+        assert!(!serde_json::to_string(&r).unwrap().contains("golden_age"),
+            "inactive golden age omitted from wire");
+        r.golden_age_active = true;
+        r.golden_age_turns = 8;
+        let json = serde_json::to_string(&r).unwrap();
+        assert!(json.contains("\"golden_age_active\":true"), "json={json}");
+        assert!(json.contains("\"golden_age_turns\":8"), "json={json}");
+        let back: ResourceView = serde_json::from_str(&json).unwrap();
+        assert_eq!(r, back);
+    }
+
     #[test]
     fn unit_posture_serialized_only_when_active() {
         let mut u = UnitView {