docs(@projects/@magic-civilization): 🏛️ p3-28 — modular turn architecture objective (cycle + registry done)

Records the foundation refactor: dep-cycle break (5ee312e45) + end-of-turn phase registry
(af41ea10a) done; boot-config DRY (3 layers → 1 Rust-native loader) + registry-widening
remaining.

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

.project/objectives/p3-28-modular-turn-architecture.md

@@ -0,0 +1,38 @@
+---
+id: p3-28
+title: Modular turn architecture — break dep cycle, phase registry, boot-config DRY
+priority: p3
+scope: game1
+owner: warcouncil
+status: partial
+updated_at: 2026-06-26
+---
+
+## Summary
+
+The per-subsystem sprawl noticed while porting climate/events/happiness/healing/ecology
+revealed three SOLID/DRY/DIP debts. "Foundation first" tackled the layering + phase pieces.
+
+## Acceptance
+
+- [x] **Break the mc-turn↔mc-ecology dependency cycle (DIP)** ✅ 90e5c3841 — mc-ecology pulled
+  in the whole mc-mapgen crate only to reach `mc_mapgen::seed`, itself a re-export of
+  `mc_core::seed`. Repointed to mc_core; dropped the mc-mapgen dep. Cycle root cut.
+- [x] **End-of-turn phase registry (OCP)** ✅ ba60fe2d4 — `mc-turn::sim_phases::END_OF_TURN_PHASES`
+  (ordered `fn(&mut GameState)` data list). Ecology moved out of its mc-player-api
+  apply_end_turn special-case into mc-turn::step; all phases now in one crate. Extending the
+  living world = one registry line + a phase module, no step() edit.
+- [ ] **Boot-config DRY (Opportunity A)** — collapse the 6 `set_*_json` FFI setters + 9
+  `_apply_*` GDScript harness loaders + N `#[serde(skip)]` GameState fields into one
+  Rust-native `boot_from_resources(path)` reading `public/resources/*` directly (Rust already
+  does this in tests). Removes GDScript-shuttling-data (Rail-3 smell); single source of truth
+  = the JSON files. NOT YET DONE (was the separate option 2).
+- [ ] **Widen the registry** — optionally fold climate (convert the method to a free fn) +
+  happiness into the registry / a positioned-phase model so the whole turn sequence is data.
+
+## Notes
+
+Created 2026-06-26. The registry currently covers the contiguous end-of-turn world-sim phases
+(ecology, healing); climate stays a TurnProcessor method (shares climate helpers) and happiness
+stays positioned post-economy — both deliberately, to avoid risky reordering. The big remaining
+win is the boot-config DRY (3 layers → 1 Rust loader).