docs: update architecture gate progress

BUILD_IN_PUBLIC_PLAN.md:
- Mark systems gate items deterministic clock and headless checksum
  as complete; remaining gate work stays flagged as in-progress
- Rename TaskZone references to ActivityMarkers for consistency

LEARNING_ROADMAP.md:
- Add architecture gate progress note: first deterministic slice
  (SimulationClock, seeded streams, headless checksum) is implemented
- Update recommended implementation order to reflect shifted priorities

PROJECT_CONTEXT.md:
- Note that farm and forest markers have been deleted from main.tscn
- Update activity marker description (4 remaining: guard/study/rest/food)
- Add SimulationClock.gd and deterministic_simulation_test.gd to repo map
- Update technical debt: randomness is now seeded but RNG state is not
  yet serialized; clock is explicit but orchestration still lives on scene tree
- Gate status updated with completed first-slice summary

RESOURCE_NODE_MIGRATION.md:
- Mark Phase 4b (player parity) complete
- Phase 6 renamed from 'remove zone model' to 'replace activity markers'
  with progress note: TaskZone container and FarmZone/ForestZone deleted
- Update divergences to note farm/forest scene nodes have been removed

docs/BUILD_IN_PUBLIC_PLAN.md

@@ -41,7 +41,8 @@ Do not redo these tasks:
 - hunger, energy, starvation, death, task scoring, and task duration;
 - task-change and village-change signals;
 - visual NPC navigation and arrival reporting;
-- farm, forest, food, guard, study, and rest markers;
+- finite berry/tree ResourceNodes plus food, guard, study, and rest activity
+  markers;
 - aggregate village UI;
 - initial tree assets;
 - a baked navigation region for the current flat test area.
@@ -61,7 +62,7 @@ Main
 ├── SimulationManager
 ├── WorldViewManager
 ├── ActiveNPCs
-├── TaskZone markers
+├── ActivityMarkers
 ├── WorldEnvironment
 └── UI
 ```
@@ -93,7 +94,7 @@ Main
 │   │   └── ResourceNodes
 │   │       ├── BerryBush instances
 │   │       └── Tree instances
-│   ├── LegacyTaskMarkers              temporary non-resource activities
+│   ├── LegacyActivityMarkers          temporary non-resource activities
 │   │   ├── FoodZone
 │   │   ├── GuardZone
 │   │   ├── StudyZone
@@ -290,7 +291,7 @@ Create `world/jajce/JajceWorld.tscn` with:
 - placeholder `VillageRoot`;
 - placeholder `FoliageRoot`;
 - a navigation region;
-- resource-node containers plus temporary fallback markers;
+- resource-node containers plus temporary activity markers;
 - lighting and environment.
 
 Create `JajceLookdev.tscn` that instances `JajceWorld` and adds a temporary
@@ -351,14 +352,14 @@ river, and waterfall silhouettes plus a temporary baked navigation loop. The
 Terrain3D seed remains flat; sculpt refinement and the final bake resume only
 after the architecture gate.
 
-### Systems gate — Harden simulation authority ⏭ next
+### Systems gate — Harden simulation authority 🔶 in progress
 
 After the scaffold, greybox, and navigation spike prove the world shape, pause
 visual production and complete the mandatory architecture gate from the
 learning roadmap:
 
-- deterministic clock and seeded randomness;
-- fixed-seed headless scenarios and final-state checksum;
+- deterministic clock and seeded randomness; ✅
+- fixed-seed headless scenarios and final-state checksum; ✅
 - versioned serializable NPC, village, and resource records;
 - resource amount and reservation authority outside scene nodes;
 - stable action/profession IDs and initial definitions;
@@ -406,7 +407,7 @@ Once the world composition is stable:
 3. Place or move bushes and trees under
    `JajceWorld/WorldObjects/ResourceNodes` while preserving stable IDs.
 4. Reconnect only remaining non-resource activity markers under
-   `JajceWorld/LegacyTaskMarkers`.
+   `JajceWorld/LegacyActivityMarkers`.
 5. Bake navigation for the new walkable area.
 6. Test each existing task from multiple spawn positions.
 7. Verify task arrival still transitions from traveling to working.