feat(client): district morphology generation overlay in the Atlas (T-1046, D-226)

Client half — the cascade's district tier is now visible in the Atlas map.

- protocol.gd: decode the district_grid field from AtlasLayerResponse.
- atlas_viewer.gd: a gen_district ('MRPH') toggle in OVERLAY_DEFS + the
  district-grid generation state (set/get) + wire it from the Ready response.
- atlas_marker_overlay.gd: _draw_gen_district() paints the coarse cols×rows grid,
  each cell coloured by its MorphologyZone discriminant (D-239 §6, 17-zone
  palette), semi-transparent under the Layer-1 line overlays. Planetary map view
  (not the 2km on-demand districts — those are Phase 5 in-world).

gdUnit4 test: overlay registered + district grid round-trips through the viewer
and the protocol decode. Visual tuning of the palette can follow once eyeballed
in the running Atlas.

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

client/scripts/protocol/protocol.gd

@@ -787,6 +787,7 @@ static func atlas_response_from_raw(raw: Variant) -> Variant:
 		"status": status,
 		"error": error,
 		"layer1": raw.get("layer1"),
+			"district_grid": raw.get("district_grid"),
 	}
 
 

client/tests/test_atlas_overlays.gd

@@ -9,7 +9,29 @@ func test_generation_overlays_registered() -> void:
 	var ids: Array = []
 	for d: Dictionary in AtlasViewer.OVERLAY_DEFS:
 		ids.append(d["id"])
-	assert_that(ids).contains(["gen_l1_rivers", "gen_l1_basins", "gen_l1_attractors"])
+	assert_that(ids).contains(
+		["gen_l1_rivers", "gen_l1_basins", "gen_l1_attractors", "gen_district"]
+	)
+
+
+## T-1046: the district/morphology grid round-trips through the viewer and the
+## protocol decode surfaces it; referencing AtlasMarkerOverlay compiles the draw.
+func test_district_grid_round_trips() -> void:
+	var v: AtlasViewer = auto_free(AtlasViewer.new())
+	assert_that(v.get_generation_district_grid()).is_null()
+	var grid := {
+		"cols": 2,
+		"rows": 1,
+		"morphology": PackedByteArray([8, 14]),
+		"elev_q": PackedByteArray([10, 90]),
+	}
+	v.set_generation_district_grid(grid)
+	assert_that(v.get_generation_district_grid()).is_equal(grid)
+	# The decoded response dict carries the district_grid key (protocol.gd, T-1046).
+	var decoded: Variant = Protocol.atlas_response_from_raw(
+		{"body_id": "GJ1c", "status": "Ready", "district_grid": grid}
+	)
+	assert_that((decoded as Dictionary).get("district_grid")).is_equal(grid)
 
 
 func test_generation_data_round_trips() -> void:

client/ui/implant/apps/atlas/atlas_marker_overlay.gd

@@ -109,6 +109,13 @@ func _draw() -> void:
 	if viewer.is_overlay_visible("corp_presence"):
 		_draw_corp_presence(markers)
 
+	# Generation: district morphology grid (T-1046, D-226) — coarse area fill,
+	# drawn under the Layer-1 line/point overlays.
+	if viewer.is_overlay_visible("gen_district"):
+		var grid: Variant = viewer.get_generation_district_grid()
+		if grid is Dictionary:
+			_draw_gen_district(grid, tex_w, tex_h)
+
 	# Generation-cascade layers (#960, D-225) — from the proxied Layer1Output.
 	# Draw order: basins (area) under rivers under attractors (point anchors).
 	var layer1: Variant = viewer.get_generation_layer1()
@@ -385,6 +392,60 @@ func _gen_pos(rc: Variant) -> Vector2:
 	return Vector2(float(rc[1]) / _gen_grid_w * _gen_tex_w, float(rc[0]) / _gen_grid_h * _gen_tex_h)
 
 
+## District morphology grid (T-1046, D-226). A coarse `cols × rows` area fill —
+## each cell coloured by its MorphologyZone discriminant (D-239 §6), semi-
+## transparent so the heightmap reads through. Planetary-scale map view (NOT the
+## 2 km on-demand districts, which are Phase 5 in-world).
+func _draw_gen_district(grid: Dictionary, tex_w: float, tex_h: float) -> void:
+	var cols: int = int(grid.get("cols", 0))
+	var rows: int = int(grid.get("rows", 0))
+	if cols <= 0 or rows <= 0:
+		return
+	var morphology: Variant = grid.get("morphology")
+	if not morphology is PackedByteArray:
+		return
+	var cw: float = tex_w / float(cols)
+	var ch: float = tex_h / float(rows)
+	var n: int = morphology.size()
+	for ry in range(rows):
+		for rx in range(cols):
+			var i: int = ry * cols + rx
+			if i >= n:
+				continue
+			# +0.5 overdraw avoids hairline seams between adjacent cells.
+			draw_rect(Rect2(rx * cw, ry * ch, cw + 0.5, ch + 0.5), _morphology_color(int(morphology[i])))
+
+
+## MorphologyZone discriminant → overlay colour (D-239 §6 order). ~0.55 alpha so
+## the heightmap shows through: water blues, plains greens, uplands greys/browns,
+## volcanic dark red.
+const MORPHOLOGY_COLORS: Array = [
+	Color(0.10, 0.20, 0.45, 0.55),  # 0  OpenOcean
+	Color(0.20, 0.40, 0.65, 0.55),  # 1  Lake
+	Color(0.45, 0.55, 0.50, 0.55),  # 2  TidalFlat
+	Color(0.85, 0.78, 0.45, 0.55),  # 3  DuneStrand
+	Color(0.50, 0.50, 0.55, 0.55),  # 4  CliffCoast
+	Color(0.30, 0.40, 0.50, 0.55),  # 5  Fjord
+	Color(0.40, 0.65, 0.60, 0.55),  # 6  Delta
+	Color(0.30, 0.55, 0.55, 0.55),  # 7  Estuarine
+	Color(0.30, 0.60, 0.30, 0.55),  # 8  AlluvialPlain
+	Color(0.45, 0.70, 0.40, 0.55),  # 9  RiverBank
+	Color(0.35, 0.60, 0.50, 0.55),  # 10 MeanderReach
+	Color(0.55, 0.60, 0.45, 0.55),  # 11 BraidedPlain
+	Color(0.50, 0.55, 0.30, 0.55),  # 12 ValleyFloor
+	Color(0.55, 0.45, 0.30, 0.55),  # 13 MountainPass
+	Color(0.80, 0.82, 0.85, 0.55),  # 14 Alpine
+	Color(0.45, 0.15, 0.12, 0.55),  # 15 Volcanic
+	Color(0.25, 0.45, 0.40, 0.55),  # 16 Wetland
+]
+
+
+func _morphology_color(zone: int) -> Color:
+	if zone >= 0 and zone < MORPHOLOGY_COLORS.size():
+		return MORPHOLOGY_COLORS[zone]
+	return Color(0.5, 0.5, 0.5, 0.4)
+
+
 func _draw_gen_rivers(layer1: Dictionary) -> void:
 	var rn: Variant = layer1.get("river_network")
 	if not rn is Dictionary:

client/ui/implant/apps/atlas/atlas_viewer.gd

@@ -139,6 +139,12 @@ const OVERLAY_DEFS: Array = [
 		"group": "toggle",
 		"tooltip": "Layer 1 — geographic attractors (generation overlay, #960)."
 	},
+	{
+		"id": "gen_district",
+		"label": "MRPH",
+		"group": "toggle",
+		"tooltip": "District morphology zones (generation overlay, T-1046/D-226)."
+	},
 ]
 
 # ── Context (set by show_body) ─────────────────────────────────────────────────
@@ -150,6 +156,7 @@ var _implant_theme = null
 var _heightmap_texture: Texture2D = null
 var _markers: Dictionary = {}
 var _generation_layer1: Variant = null  # #960: Layer1Output from the proxy (D-225)
+var _generation_district_grid: Variant = null  # T-1046: coarse DistrictGridLayer (D-226)
 var _gen_pending: bool = false  # #960: awaiting a Layer1 response (re-polls on Pending)
 var _gen_retries: int = 0
 var _grid_w: float = 512.0
@@ -298,6 +305,18 @@ func get_generation_layer1() -> Variant:
 	return _generation_layer1
 
 
+## T-1046: store the coarse district/morphology grid (DistrictGridLayer) from the
+## proxy and redraw. The marker overlay reads it via get_generation_district_grid().
+func set_generation_district_grid(grid: Variant) -> void:
+	_generation_district_grid = grid
+	if _overlay_node:
+		_overlay_node.queue_redraw()
+
+
+func get_generation_district_grid() -> Variant:
+	return _generation_district_grid
+
+
 ## #960: request the body's Layer-1 cascade output from the server proxy.
 ## No-op in test mode (SimBridge has no server connection) — the overlays
 ## simply stay empty, which is the correct serverless behavior.
@@ -322,6 +341,7 @@ func _on_atlas_layers_received(response: Dictionary) -> void:
 			_gen_retries = 0
 			_set_gen_indicator(false)
 			set_generation_layer1(response.get("layer1"))
+			set_generation_district_grid(response.get("district_grid"))
 		"Pending":
 			if _gen_retries < GEN_MAX_RETRIES:
 				_gen_retries += 1