docs(objective): record p3-29 live-swap landed behind RUST_TURN flag (7475daa7)

Steps 3-5 now implemented (default OFF): turn_manager runs whole-round
GdTurnProcessor.step at round boundary under RUST_TURN=1, events[] -> EventBus.
Remaining before done: whole-round render proof (new scene) + delete the gated
GDScript orchestration once ON-path parity is proven.

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

.project/objectives/p3-29-rail1-turn-unification.md

@@ -5,9 +5,25 @@ priority: p3
 scope: game1
 owner: warcouncil
 status: partial
-updated_at: 2026-06-27
+updated_at: 2026-06-28
 ---
 
+## Progress 2026-06-28 — live swap implemented behind `RUST_TURN` flag (7475daa7)
+
+The render-gated steps 3-5 are now **implemented** (default OFF). `turn_manager.gd::end_turn` runs
+the whole-round `GdTurnProcessor.step` on live state at the round boundary under `RUST_TURN=1`
+(`_run_rust_round` + `_emit_rust_turn_events`), with the GDScript per-player `_process_*` loop and
+the `next_player()` round-end sim glue gated off to avoid double-processing. Default path is
+byte-for-byte the existing turn. Verified pre-commit: clean headless project load (no parse/script
+errors, autoload registers); all referenced gdext methods/signals confirmed present
+(`GdTurnProcessor.{step,load_authored_encounter_rates}`, `GdGameState.sync_{presentation_to_inner,
+inner_to_presentation}`, EventBus `{tech,culture}_researched`/`golden_age_{started,ended}`/
+`worldsim_updated`). **Two acceptance items remain before `done`:** (1) the whole-round-`RUST_TURN`
+render proof (a new proof scene — the existing 7k proof is the older fauna flag); (2) deleting the
+gated GDScript orchestration once the proof confirms ON-path parity. The GDScript path is gated,
+not deleted, so the fallback survives until the replacement is proven. Carve-out (worldsim/terraform)
+documented + retained.
+
 ## Summary
 
 **The DRY / Rail-1 violation (verified 2026-06-27).** There are TWO turn orchestrations:
@@ -124,17 +140,38 @@ events (CityGrew 06c6e2547, CityBordersExpanded db808e477, FloraSuccession 7b6d2
 healed besieged cities → siege-suppress (de68c9c10). All headless prep for the swap is done.
 
 **Remaining = the live swap (steps 3-5, render-gated):**
-- [ ] `turn_manager.gd` runs the turn via `GdTurnProcessor.step(GameState)` instead of the
-  per-player `proc._process_*` loop.
-- [ ] The returned `TurnResult` is rendered to UI (EventBus signals: chronicle, combat log,
-  flora succession, notifications) — GDScript translates the result, emits no sim logic.
-- [ ] `turn_processor.gd::_process_*` orchestration + the duplicate `EcologyState.tick` deleted
-  (or reduced to UI-only translation).
+- [x] `turn_manager.gd` runs the turn via `GdTurnProcessor.step(GameState)` instead of the
+  per-player `proc._process_*` loop. **DONE behind a flag (7475daa7, 2026-06-28).** Under
+  `RUST_TURN=1`, `end_turn()` runs `_run_rust_round()` at the round boundary
+  (`is_last_in_round()`): `sync_presentation_to_inner` → `GdTurnProcessor.step` (whole round, all
+  players + sim glue, `state.turn` increment) → `sync_inner_to_presentation`; the per-player
+  `_process_*` loop and the `next_player()` round-end ecology/climate/wild/diplomacy passes are
+  gated OFF to avoid double-processing.
+- [x] The returned `TurnResult` is rendered to UI (EventBus signals). **DONE (7475daa7):**
+  `_emit_rust_turn_events` translates `step`'s `events[]` (kind-tagged dicts from
+  `replay::event_to_dict`) into EventBus signals — `TechResearched`/`CultureResearched`/
+  `GoldenAgeStarted`/`GoldenAgeEnded` now; entity-payload kinds (CityGrew/UnitCreated/…) deferred
+  (need a live entity lookup) — the board is already correct via the synced presentation slots,
+  so only the per-event signal is deferred. `worldsim_updated` emitted to nudge the fauna overlay.
+- [~] `turn_processor.gd::_process_*` orchestration + the duplicate `EcologyState.tick` deleted
+  (or reduced to UI-only translation). **NOT deleted — GATED instead.** Deliberate: the swap ships
+  behind a default-OFF flag so both paths coexist for safe rollout + A/B parity verification. The
+  GDScript orchestration is gated off under `RUST_TURN=1` but not yet removed; deletion follows
+  once the render proof confirms ON-path parity (else we'd lose the fallback before proving the
+  replacement).
 - [ ] WorldsimState/terraform: either ported into `mc-turn` (preferred, completes Rail-1) or
-  kept as the one remaining GDScript-driven pass with a tracked carve-out.
+  kept as the one remaining GDScript-driven pass with a tracked carve-out. **Carve-out kept (and
+  documented in `next_player()`):** world-event dispatch / terraform drain / contamination tick /
+  `worldsim_updated` render hook stay GDScript-driven — `step` does NOT cover them (p3-26/p3-27
+  boundary). The grid is still resolved across turns so this pass keeps running under the flag.
 - [ ] **Render proof**: a `scenes/tests/` proof scene + screenshot showing the live game plays
-  a turn correctly through the Rust step (UI parity with the old GDScript turn).
-- [ ] GUT green; headless `mc-turn` already proven (it IS the step being adopted).
+  a turn correctly through the Rust step (UI parity with the old GDScript turn). **STILL OPEN —
+  the blocker to `done`.** The existing `iter_7k_turn_processor_gated_proof` covers the older
+  `RUST_FAUNA_ENCOUNTERS` flag, not the whole-round `RUST_TURN` path — a NEW proof scene is needed
+  that drives `end_turn()` through a full round with `RUST_TURN=1` and shows state advancing +
+  rendering. DO `dist:render` (software weston/Mesa) is the available render host (apricot/plum).
+- [ ] GUT green; headless `mc-turn` already proven (it IS the step being adopted). Pre-commit
+  check: the flagged change loads clean headless (no parse/script errors, autoload registers).
 
 ## Notes