fix(ui): address PR #118 review — 5 items

- Preload stance icons at _ready() into cache Dictionary
- Null-guard shader + theme loads with push_error() + early return
- Guard _icon_mat.set_shader_parameter inside if _icon_mat:
- Icon size 18→20px per D-086, container height 44→46px to fit
- Add _apply_stance test coverage (known + unknown stance)

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

client/tests/test_ui_framework_sprint15.gd

@@ -313,3 +313,33 @@ func test_tile_renderer_skips_nonzero_z() -> void:
 	# z=1 and z=2 tiles should NOT be present (-1 = no cell)
 	assert_that(tile_renderer.get_cell_source_id(Vector2i(1, 0))).is_equal(-1)
 	assert_that(tile_renderer.get_cell_source_id(Vector2i(3, 0))).is_equal(-1)
+
+
+# -------------------------------------------------------------------------
+# Stance indicator icon tests (#787)
+# -------------------------------------------------------------------------
+
+func test_stance_indicator_applies_known_stance() -> void:
+	# #787: _apply_stance updates icon + label for each known stance.
+	var scene := MAIN_SCENE
+	_instance = scene.instantiate()
+	auto_free(_instance)
+	add_child(_instance)
+
+	var si = _instance.get_node_or_null("UILayer/StanceIndicator")
+	assert_that(si).is_not_null()
+	si._apply_stance("Careful")
+	assert_that(si.get_current_stance()).is_equal("Careful")
+
+
+func test_stance_indicator_unknown_stance_no_crash() -> void:
+	# #787: Unknown stance falls back gracefully — no crash, no texture change.
+	var scene := MAIN_SCENE
+	_instance = scene.instantiate()
+	auto_free(_instance)
+	add_child(_instance)
+
+	var si = _instance.get_node_or_null("UILayer/StanceIndicator")
+	assert_that(si).is_not_null()
+	si._apply_stance("InvalidStance")
+	assert_that(si.get_current_stance()).is_equal("InvalidStance")