Add session shell and close world presentation follow-ups

Session shell
- Startup venue menu (src/game/ui/start_menu.gd): keyboard + mouse, replaces
  the live-shift boot and V as the player-facing venue path (V stays a debug bind).
- Pause overlay on Esc (src/game/ui/pause_overlay.gd): resume, restart shift,
  settings, quit to menu.
- Settings panel (src/game/ui/settings_panel.gd): mouse look sensitivity and
  HUD font scale, persisted via Save into user://settings.json and loaded on boot.
- Shift review "Run another shift" now returns to the venue menu.
- New smoke: src/test/smoke_session_shell.gd (menu -> shift -> pause -> settings
  -> menu), passes headless and windowed.

World and presentation
- Skyline backdrop restored with a transparent asset and an alpha-scissor
  unshaded material; fixes the opaque black slab from the earlier attempt and
  the unimported texture path.
- Steps and landing are a StaticBody3D with per-tread colliders, so the guard
  and NPCs walk up instead of clipping through.
- Marquee Label3D scaled up (72 -> 160) so STEP LINE reads from the sidewalk.
- Focus torus and name tag enlarged for 2-3 m readability.
- Routine traffic despawns after an idle lifetime (NpcAvatar.ephemeral), so the
  16-NPC cap no longer fills with standers; authored events stay for the shift.

Docs and tests
- PLAN.md test/CI section corrected to the custom headless runner and Gitea Actions.
- README controls table, smoke checklist, test count, and status lists refreshed.
- TODO/DONE/MEMORY updated; completed sections moved to DONE.md.
- Headless suite 77 -> 88 passing (settings round-trip, step colliders, skyline
  alpha, session-shell UI behavior, traffic lifetime).

src/test/tests/test_persistence.gd

@@ -30,3 +30,24 @@ func test_load_returns_array_when_empty_or_missing() -> bool:
 	var ok := TestUtils.check(results is Array, "load_shift_results always returns Array")
 	save.free()
 	return ok
+
+func test_settings_round_trip() -> bool:
+	var save := _save_instance()
+	var err: int = save.save_settings({"look_sensitivity": 0.0035, "hud_font_scale": 1.25})
+	var a := TestUtils.check_eq(err, OK, "save_settings succeeds")
+	var loaded: Dictionary = save.load_settings()
+	var b := TestUtils.check(is_equal_approx(float(loaded.get("look_sensitivity", 0.0)), 0.0035), "round-trips sensitivity")
+	var c := TestUtils.check(is_equal_approx(float(loaded.get("hud_font_scale", 0.0)), 1.25), "round-trips font scale")
+	# Restore defaults so later runs are not affected.
+	save.save_settings(save.DEFAULT_SETTINGS)
+	save.free()
+	return a and b and c
+
+func test_settings_defaults_present() -> bool:
+	var save := _save_instance()
+	var defaults: Dictionary = save.load_settings()
+	var ok := TestUtils.check(
+		defaults.has("look_sensitivity") and defaults.has("hud_font_scale"),
+		"settings have documented defaults")
+	save.free()
+	return ok

src/test/tests/test_session_shell.gd

@@ -0,0 +1,100 @@
+extends RefCounted
+## Session shell (start menu, pause overlay, settings) and routine-traffic
+## despawn. These are headless-shape tests: they instantiate the UI scripts and
+## check state transitions rather than rendering.
+
+const StartMenu := preload("res://src/game/ui/start_menu.gd")
+const PauseOverlay := preload("res://src/game/ui/pause_overlay.gd")
+const SettingsPanel := preload("res://src/game/ui/settings_panel.gd")
+const NpcAvatar := preload("res://src/game/npc_avatar.gd")
+
+func test_start_menu_lists_all_venues() -> bool:
+	var menu: Node = StartMenu.new()
+	# Buttons are created in _ready; build them without a tree by calling _build.
+	menu._build()
+	var ids: Array[String] = []
+	for venue in StartMenu.VENUES:
+		ids.append(str(venue["id"]))
+	var a := TestUtils.check_eq(ids.size(), 3, "three venues offered")
+	var b := TestUtils.check(ids.has("hollywood_building"), "Hollywood Blvd present")
+	var c := TestUtils.check(ids.has("joke_shop"), "Joke Shop present")
+	var d := TestUtils.check(ids.has("tv_studio"), "TV Studio present")
+	menu.free()
+	return a and b and c and d
+
+func test_start_menu_emits_selected_venue() -> bool:
+	var menu: Node = StartMenu.new()
+	menu._build()
+	var got := {"id": ""}
+	menu.venue_selected.connect(func(id): got["id"] = id)
+	menu._on_venue_pressed(1)
+	var a := TestUtils.check_eq(got["id"], "joke_shop", "clicking venue 2 selects the Joke Shop")
+	var b := TestUtils.check(not menu.visible, "menu closes after a venue is picked")
+	menu.free()
+	return a and b
+
+func test_start_menu_clamps_focus() -> bool:
+	var menu: Node = StartMenu.new()
+	menu._build()
+	menu._focus_index(-5)
+	var low: int = menu._index
+	menu._focus_index(99)
+	var high: int = menu._index
+	menu.free()
+	return TestUtils.check_eq(low, 0, "focus clamps at the top") \
+		and TestUtils.check_eq(high, StartMenu.VENUES.size() - 1, "focus clamps at the bottom")
+
+func test_pause_overlay_buttons_emit() -> bool:
+	var overlay: Node = PauseOverlay.new()
+	overlay._build()
+	var seen: Array[String] = []
+	overlay.resume_requested.connect(func(): seen.append("resume"))
+	overlay.restart_requested.connect(func(): seen.append("restart"))
+	overlay.settings_requested.connect(func(): seen.append("settings"))
+	overlay.quit_to_menu_requested.connect(func(): seen.append("menu"))
+	for node_name in ["ResumeButton", "RestartButton", "SettingsButton", "MenuButton"]:
+		var button: Button = overlay.find_child(node_name, true, false) as Button
+		if button:
+			button.pressed.emit()
+	overlay.free()
+	var expected := ["resume", "restart", "settings", "menu"]
+	return TestUtils.check_eq(seen, expected, "pause overlay exposes resume/restart/settings/menu")
+
+func test_settings_panel_persists_values() -> bool:
+	var panel: Node = SettingsPanel.new()
+	panel._build()
+	panel.open({"look_sensitivity": 0.0022, "hud_font_scale": 1.0})
+	panel._on_sensitivity_changed(0.004)
+	panel._on_font_scale_changed(1.3)
+	var applied := {"settings": {}}
+	panel.applied.connect(func(s): applied["settings"] = s)
+	panel._on_apply()
+	var s: Dictionary = applied["settings"]
+	var a := TestUtils.check(is_equal_approx(float(s.get("look_sensitivity", 0.0)), 0.004), "sensitivity applied")
+	var b := TestUtils.check(is_equal_approx(float(s.get("hud_font_scale", 0.0)), 1.3), "font scale applied")
+	var c := TestUtils.check(not panel.visible, "panel closes on apply")
+	# Restore defaults written by the apply call.
+	if Save:
+		Save.save_settings(Save.DEFAULT_SETTINGS)
+	panel.free()
+	return a and b and c
+
+func test_settings_panel_cancel_discards() -> bool:
+	var panel: Node = SettingsPanel.new()
+	panel._build()
+	panel.open({"look_sensitivity": 0.0022, "hud_font_scale": 1.0})
+	panel._on_sensitivity_changed(0.005)
+	var applied := {"count": 0}
+	panel.applied.connect(func(_s): applied["count"] += 1)
+	panel._on_cancel()
+	var a := TestUtils.check(not panel.visible, "cancel closes the panel")
+	var b := TestUtils.check_eq(applied["count"], 0, "cancel does not apply")
+	panel.free()
+	return a and b
+
+func test_routine_traffic_is_ephemeral() -> bool:
+	var avatar: Node = NpcAvatar.new()
+	var a := TestUtils.check(avatar.ephemeral, "avatars default to ephemeral")
+	var b := TestUtils.check(avatar.lifetime_s > 0.0, "ephemeral traffic has a lifetime")
+	avatar.free()
+	return a and b

src/test/tests/test_world.gd

@@ -78,6 +78,36 @@ func test_asset_textures_present_and_pow2() -> bool:
 			return TestUtils.fail("asset not power-of-two: %s (%dx%d)" % [path, w, h])
 	return true
 
+func test_steps_have_colliders() -> bool:
+	## Steps were visual-only and the guard walked through them (TODO).
+	var root := Node3D.new()
+	WorldBuilder.new(root).build()
+	var steps := root.find_child("Steps", true, false)
+	var a := TestUtils.check(steps != null, "Steps node exists")
+	var b := TestUtils.check(steps is StaticBody3D, "Steps are a physics body")
+	var shape_count := 0
+	if steps is StaticBody3D:
+		var body := steps as StaticBody3D
+		shape_count = body.get_shape_owners().size()
+	var c := TestUtils.check(shape_count >= 5, "four treads + landing have colliders (got %d)" % shape_count)
+	root.free()
+	return a and b and c
+
+func test_skyline_backdrop_uses_alpha() -> bool:
+	## The opaque skyline texture made the plane render as a black slab (TODO).
+	var root := Node3D.new()
+	var builder := WorldBuilder.new(root)
+	builder.build()
+	var backdrop := root.find_child("SkylineBackdrop", true, false)
+	var a := TestUtils.check(backdrop != null, "SkylineBackdrop exists")
+	var mat: StandardMaterial3D = builder._skyline_mat
+	var b := TestUtils.check(mat != null, "skyline material captured")
+	var c := TestUtils.check(
+		mat != null and mat.transparency != BaseMaterial3D.TRANSPARENCY_DISABLED,
+		"skyline material uses alpha, not an opaque slab")
+	root.free()
+	return a and b and c
+
 func test_door_indicator_built() -> bool:
 	var root := Node3D.new()
 	var builder := WorldBuilder.new(root)