feat(@projects/@magic-civilization): 📋 p3-26 gap 2 — event-config loader (mc-climate::events)

Next brick of the events port: load per-category configs from the canonical JSON
(Rail-2, nothing hardcoded).

- EventCategoryConfig { base_frequency, severity_weights, raw } — typed dispatch inputs +
  the full JSON kept in `raw` so each per-category handler reads its own fields (tiers,
  target_terrain, becomes, aerosol_strength) without modeling all 12 shapes up front.
- load_event_configs(dir) reads public/resources/events/<category>.json (category =
  filename stem; skips *.schema / cross_triggers / events). Test parses the real
  wildfire.json (base_frequency 0.04, severity_weights, target_terrain ∋ "forest").

mc-climate events 5/5. Next: dispatch (process_events using category_fires + roll_severity)
+ per-category handlers (wildfire first — burn forest in radius, transform biome) + wire
into the mc-turn climate phase. Tile-picking will use a Rust-deterministic RNG (the
headless sim needs internal determinism, not byte-match with the live game's Godot RNG;
the dispatch GATE already matches GDScript bit-for-bit).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/simulator/crates/mc-climate/src/events.rs

@@ -48,6 +48,69 @@ pub fn category_fires(base_frequency: f64, channel: f64, turn_seed: f64) -> bool
     hash_noise(channel, 0.0, turn_seed) < base_frequency
 }
 
+/// One natural-event category's config, loaded from `public/resources/events/<cat>.json`.
+/// `base_frequency` + `severity_weights` drive the dispatch (typed); `raw` keeps the full
+/// JSON so each per-category handler can read its specific fields (tiers, target_terrain,
+/// becomes, aerosol_strength, …) without this struct having to model all 12 shapes.
+#[derive(Debug, Clone)]
+pub struct EventCategoryConfig {
+    pub base_frequency: f64,
+    pub severity_weights: Vec<i32>,
+    pub raw: serde_json::Value,
+}
+
+/// Load per-category event configs from `public/resources/events/<category>.json`. The
+/// category name is the filename stem. Non-category files (`*.schema`, `cross_triggers`,
+/// `events`) are skipped, as are files lacking `base_frequency`/`severity_weights`. The
+/// per-category JSON is the canonical content store (Rail-2); nothing is hardcoded here.
+pub fn load_event_configs(
+    events_dir: &std::path::Path,
+) -> std::collections::BTreeMap<String, EventCategoryConfig> {
+    let mut out = std::collections::BTreeMap::new();
+    let entries = match std::fs::read_dir(events_dir) {
+        Ok(e) => e,
+        Err(_) => return out,
+    };
+    for entry in entries.flatten() {
+        let path = entry.path();
+        if path.extension().and_then(|e| e.to_str()) != Some("json") {
+            continue;
+        }
+        let stem = match path.file_stem().and_then(|s| s.to_str()) {
+            Some(s) => s.to_string(),
+            None => continue,
+        };
+        if stem.ends_with(".schema") || stem == "cross_triggers" || stem == "events" {
+            continue;
+        }
+        let text = match std::fs::read_to_string(&path) {
+            Ok(t) => t,
+            Err(_) => continue,
+        };
+        let val: serde_json::Value = match serde_json::from_str(&text) {
+            Ok(v) => v,
+            Err(_) => continue,
+        };
+        let base_frequency = val.get("base_frequency").and_then(|v| v.as_f64());
+        let weights = val.get("severity_weights").and_then(|v| v.as_array());
+        if let (Some(bf), Some(w)) = (base_frequency, weights) {
+            let severity_weights = w
+                .iter()
+                .filter_map(|x| x.as_i64().map(|n| n as i32))
+                .collect();
+            out.insert(
+                stem,
+                EventCategoryConfig {
+                    base_frequency: bf,
+                    severity_weights,
+                    raw: val,
+                },
+            );
+        }
+    }
+    out
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -95,4 +158,34 @@ mod tests {
         assert!(category_fires(1.0, 10.0, 1.0));
         assert!(!category_fires(0.0, 10.0, 1.0));
     }
+
+    #[test]
+    fn load_event_configs_parses_real_categories() {
+        let dir = std::path::Path::new(env!("CARGO_MANIFEST_DIR"))
+            .ancestors()
+            .nth(2)
+            .expect("workspace root")
+            .join("public/resources/events");
+        let cfgs = load_event_configs(&dir);
+        assert!(!cfgs.is_empty(), "should load event categories from {dir:?}");
+        let wf = cfgs.get("wildfire").expect("wildfire config present");
+        assert!(
+            (wf.base_frequency - 0.04).abs() < 1e-9,
+            "wildfire base_frequency = {}",
+            wf.base_frequency
+        );
+        assert!(!wf.severity_weights.is_empty(), "severity_weights parsed");
+        let tt = wf
+            .raw
+            .get("target_terrain")
+            .and_then(|v| v.as_array())
+            .expect("wildfire target_terrain in raw");
+        assert!(
+            tt.iter().any(|t| t.as_str() == Some("forest")),
+            "wildfire targets forest"
+        );
+        // Non-category files are not loaded as categories.
+        assert!(!cfgs.contains_key("cross_triggers"));
+        assert!(!cfgs.contains_key("events"));
+    }
 }