docs(@projects/@magic-civilization): 📝 update objective with bug fix details

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

.project/objectives/p2-10l-followup-gdai-set-map.md

@@ -7,7 +7,7 @@ scope: game1
 category: simulation
 owner: simulator-infra
 created: 2026-05-14
-updated_at: 2026-05-14b
+updated_at: 2026-05-15
 blocked_by: []
 follow_ups: [p2-10l]
 ---
@@ -103,6 +103,32 @@ and verify GUT passes.
 - ☐ `bash tools/gut-headless.sh` reports 0 failures attributable to
   cluster #2 — requires apricot run; deferred to ACS/CI sweep.
 
+## 2026-05-15 — coord-space producer fix
+
+Production runtime exposed a deeper bug after the `update_tile` coordinate
+fix (`e200634df`): `set_map` cached 960 tiles with `hex` fields written in
+offset coordinates, while `update_tile` (and `mc-ai::tactical::settle::tile_at`)
+search by **axial** `hex`. Negative axial r (e.g. `(25, -2)`), legitimately
+emitted by every EventBus signal that drives `update_tile`, was never
+present in the cache — the producer iterated an offset rectangle
+`for row in range(height): for col in range(width)` and emitted
+`"hex": [col, row]`.
+
+Fix landed in `src/game/engine/src/modules/ai/ai_turn_bridge_state.gd`:
+- `build_tactical_tiles_json` now iterates `game_map.tiles.keys()` directly
+  (axial-keyed dict, includes negative r tiles the offset rectangle missed).
+- `tile_to_dict(game_map, q, r)` renamed and documented as axial-only; the
+  emitted `hex` field is the axial pair so the linear-search contract in
+  `mc-ai::tactical::settle::tile_at` (`api-gdext/src/ai.rs:469`) matches.
+- `build_single_tile_json(q, r)` renamed; all callers in `ai_turn_bridge.gd`
+  already pass `tile.position` (axial), so no caller-side changes needed.
+
+New regression test in `api-gdext/src/ai.rs::set_map_json_roundtrip_preserves_negative_axial_r`
+pins the Rust contract: a JSON tile array carrying axial coords (including
+negative r) round-trips faithfully and `tiles.iter().find(|t| t.hex == key)`
+locates the tile. The test deliberately verifies the buggy offset pair
+`(25, 22)` is absent, so it would have failed against the prior producer.
+
 ## References
 
 - `src/simulator/api-gdext/src/ai.rs` — current `GdAiController` surface