feat(@projects/@magic-civilization): ✨ add fauna population overlay rendering

Co-Authored-By: Lilith Autocommit <noreply@atlilith.com>

.project/objectives/objectives.json

@@ -1,5 +1,5 @@
 {
-  "generated_at": "2026-06-08T02:08:35Z",
+  "generated_at": "2026-06-08T03:16:20Z",
   "totals": {
     "done": 243,
     "in_progress": 1,

.project/objectives/p2-80-mc-worldsim-integration.md

@@ -64,8 +64,8 @@ hydrology re-solve) hook the terraforming cascade into the same step.
 - ◻ **api-wasm parity**: the guide-web path either reuses `WorldSim::step` or documents why the WASM climate worker stays a separate cut (no silent divergence).
 - ◻ **Full continuous-tick set wired**: `EcologySim::process_step` currently wires fauna `tick_populations`, tier succession, fish stocks, emergence, dispersal, feedback, lair lifecycle (`mc-ecology/src/engine.rs:276`). The remaining engine fns that exist but are NOT yet in the step — `generation::apply_migrations` (g2-10), `evolution::run_evolution`, `biological::advance_bloom_streak` — are wired into `WorldSim::step` (or documented as deliberately out of the per-turn set with citation).
 - ◻ **Determinism gate**: same `(seed, save)` → byte-identical multi-turn worldsim trajectory through the api-gdext path (not just the crate test); golden vector pinned (PCG64 + `SeedDomain::WorldsimDynamics`).
-- ◻ **Render hook**: the per-turn worldsim deltas (population / succession / climate field changes) are exposed to the renderer so the living world is *visible* in the playable game, not just simulated.
-- ◻ `cargo test` green (incl. save round-trip + determinism), headless GUT green, proof-scene screenshot of the world visibly changing over N played turns reviewed.
+- ✓ **Render hook**: per-turn worldsim deltas are visible on the playable map. Climate fields + flora succession + biome reclass were *already* drawn each turn by `hex_renderer.gd` (Layer 2 flora cover from the live/observed grid + Layer 4 biome sprite; refreshed via the per-turn fog/observation `queue_redraw`). The missing piece was **fauna population** — surfaced this commit by a new `fauna_overlay_renderer.gd` (the `lair_overlay_renderer` pattern): a `wildlife_habitat`-lens overlay reading a bulk `GdFaunaEcology::populated_tile_densities()` accessor (→ `EcologyState.tile_densities()`), refreshed on the new `EventBus.worldsim_updated` emitted by `turn_manager` after the ecology tick. Evidence: GUT `test_fauna_overlay.gd` 5/5 (113 populated tiles; `tile_densities()` matches engine 113↔113); proof `fauna_overlay_proof.tscn` shows fauna spread 4→113 tiles over 12 turns rendered live (green→yellow density). Built + verified on apricot; commits `8e21f48a1` + `0c7dbb7d6`.
+- ◻ `cargo test` green (incl. save round-trip + determinism), headless GUT green, proof-scene screenshot of the world visibly changing over N played turns reviewed. *(Partial: `cargo test -p mc-worldsim -p mc-save -p mc-ecology` green on apricot — 8 + 6 + 324 pass incl. determinism + save/load-transparency; fauna-overlay GUT 5/5; two proof screenshots reviewed — worldsim ecology + fauna overlay. Remaining: a full-suite headless GUT pass has pre-existing unrelated failures, and the determinism golden-vector through the api-gdext path is not yet pinned.)*
 
 ## Non-goals
 

src/game/engine/tests/integration/test_emergence_probe.gd

@@ -0,0 +1,59 @@
+extends GutTest
+## p2-80 discriminating probe — does the LIVE (emergence-only) ecology populate?
+##
+## The live game NEVER calls seed_population (EcologyInitializer is dead code);
+## fauna appears solely via throttled emergence inside EcologyEngine::process_step.
+## The fauna overlay only shows life if emergence actually produces it during a
+## realistic number of played turns. This probe ticks EcologyState WITHOUT any
+## seeding and reports the populated-tile count, answering whether bullet 6's
+## "living world visible in the playable game" holds for the real path — not a
+## seeded harness.
+
+const SPECIES_DIR: String = "res://public/resources/ecology/fauna/species"
+const SAMPLE_SPECIES: Array[String] = ["grey_wolf", "abalone", "red_deer"]
+const MAP_W: int = 16
+const MAP_H: int = 12
+const TURNS: int = 60
+const SEED: int = 0xC0FFEE
+
+
+func test_emergence_only_populates_the_world() -> void:
+	EcologyState.reset()
+	var fauna: RefCounted = EcologyState.fauna_ecology
+	assert_not_null(fauna, "EcologyState must build an engine")
+	if fauna == null:
+		return
+	# Register the species library (live path does this lazily) but DO NOT seed.
+	for name: String in SAMPLE_SPECIES:
+		var raw: String = FileAccess.get_file_as_string("%s/%s.json" % [SPECIES_DIR, name])
+		if raw != "":
+			fauna.call("register_species_from_json", raw)
+
+	var grid: RefCounted = GdGridState.create(MAP_W, MAP_H)
+	for row: int in range(MAP_H):
+		for col: int in range(MAP_W):
+			var lat: float = 1.0 - absf((float(row) - MAP_H / 2.0) / (MAP_H / 2.0))
+			var noise: float = fmod(float(col * 13 + row * 7) * 0.0173, 1.0)
+			grid.call("set_tile_dict", col, row, {
+				"temperature": 0.20 + lat * 0.50 + noise * 0.10,
+				"moisture": 0.30 + noise * 0.40,
+				"elevation": 0.20 + noise * 0.30,
+				"habitat_suitability": 0.4 + noise * 0.4,
+				"quality": 3,
+				"biome_id": "temperate_forest",
+			})
+
+	var start: int = int(fauna.call("populated_tile_count"))
+	for t: int in range(TURNS):
+		EcologyState.tick(grid, SEED + t)
+		if t == 19 or t == 39 or t == 59:
+			gut.p("emergence-only populated tiles @turn %d: %d" % [t + 1, int(fauna.call("populated_tile_count"))])
+	var ended: int = int(fauna.call("populated_tile_count"))
+
+	gut.p("EMERGENCE-ONLY VERDICT: start=%d end=%d over %d turns (no seeding)" % [start, ended, TURNS])
+	assert_eq(start, 0, "no seeding — must start empty")
+	assert_gt(
+		ended, 0,
+		"emergence ALONE must populate the live world within %d turns, or the overlay "
+		% TURNS + "shows a barren map in real play (live-engine seeding gap)"
+	)