fix(ui): address PR #49 review — 6 warnings + 2 suggestions (#122)

Warnings fixed:
- BBCode injection (line 153): escape [ → [lb] in server text before interpolation
- sort_custom on silent-drop (line 125): sort now only runs on actual insertion/replacement
- clip_contents: add clip_contents=true to MonologueDisplay Control (overflow guard)
- confrontation tick guard (main.gd): _last_confrontation_tick deduplicates same-tick signals
- GameState decoupling: show_monologue() reads lattice_profile once and passes it through
  _show_line() → _build_line_node(); renderer no longer reaches into autoload (D-020)
- Equal-priority eviction: >= tiebreak (was >); FIFO for equal-priority queue overflow

Suggestions fixed:
- Minimum duration clamp: maxf(duration, FADE_IN_SEC + 0.1) — line survives own fade-in
- _label_text bounds check: guard against empty _visible before indexing [0]

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/tests/test_monologue_display.gd

@@ -23,6 +23,8 @@ func _make_display() -> Node:
 
 
 func _label_text(d: Node) -> String:
+	if d._visible.is_empty():
+		return ""
 	var slot_node: Node = d._visible[0].node
 	return (slot_node.get_child(0) as RichTextLabel).text
 
@@ -456,10 +458,33 @@ func test_gamestate_monologue_replaced_by_next_snapshot() -> void:
 
 # ---------------------------------------------------------------------------
 # D-049 Z-layer / canvas scope compliance
-# Monologue display must be parented to CANVAS_UI (CanvasLayer 20), not the
-# world layer. This constant check ensures it hasn't silently drifted.
+# MonologueDisplay must be parented to UILayer (CanvasLayer, layer=20).
+# Two tests: (1) constant sanity, (2) scene tree structural verification.
 # ---------------------------------------------------------------------------
 
 func test_canvas_ui_constant_is_20() -> void:
 	## D-049: CANVAS_UI = 20 is the agreed HUD layer for monologue display.
+	## Sanity check — constant must not drift from the spec.
 	assert_that(Constants.CANVAS_UI).is_equal(20)
+
+
+func test_monologue_display_parented_to_canvas_layer_20_in_main_scene() -> void:
+	## D-049: Structural verification — MonologueDisplay must be a direct child of
+	## UILayer (CanvasLayer, layer=20) in the live scene tree, not the world layer.
+	## Catches regressions where the node gets accidentally moved to InsertOverlay
+	## (layer=10) or ModalLayer (layer=30), or dropped into the world z-stack.
+	##
+	## Scene path verified: Game/UILayer/MonologueDisplay (main.tscn line 141).
+	if not ResourceLoader.exists("res://scenes/main.tscn"):
+		push_warning("TestMonologueDisplay: main.tscn not found — D-049 scene tree test skipped")
+		return
+	var scene: Node = load("res://scenes/main.tscn").instantiate()
+	auto_free(scene)
+	add_child(scene)
+
+	var mono: Node = scene.get_node_or_null("UILayer/MonologueDisplay")
+	assert_that(mono != null).is_true()
+
+	var parent: Node = mono.get_parent()
+	assert_that(parent is CanvasLayer).is_true()
+	assert_that((parent as CanvasLayer).layer).is_equal(Constants.CANVAS_UI)