Add comprehensive UI system with action bar, unit frame, and character sheet

- Created UI system in level/ui/ folder
  - Action bar with 12 ability slots (Attack, Block, Dash, Jump + 8 expansion slots)
  - Unit frame showing player portrait with health bar
  - Character sheet/spellbook (toggle with Tab) displaying stats, weapons, and abilities
  - Tab hint indicator showing how to open character sheet
  - Custom theme with golden borders and dark backgrounds

- UI Components:
  - HUD Manager autoload handles all UI initialization and player connections
  - Ability buttons with cooldown overlay and keybind display
  - Real-time health and cooldown tracking via signals
  - Scrollable character sheet with two-page layout

- Player Integration:
  - Added UI signals: dash_cooldown_updated, attack_cooldown_updated, weapon_equipped_changed
  - Mouse capture system (Escape to toggle, click to recapture)
  - Synced attack cooldown from weapons to player for UI tracking

- Updated level.gd to connect local player to HUD Manager
- Updated CLAUDE.md with git commit guidelines

level/ui/scenes/action_bar.tscn

@@ -0,0 +1,64 @@
+[gd_scene load_steps=3 format=3 uid="uid://b4h0p6nbcq35b"]
+
+[ext_resource type="Script" path="res://level/ui/scripts/action_bar.gd" id="1_script"]
+[ext_resource type="PackedScene" uid="uid://cq7xyb8n4h6yk" path="res://level/ui/scenes/ability_button.tscn" id="2_ability_button"]
+
+[node name="ActionBar" type="Control"]
+layout_mode = 3
+anchors_preset = 7
+anchor_left = 0.5
+anchor_top = 1.0
+anchor_right = 0.5
+anchor_bottom = 1.0
+offset_left = -400.0
+offset_top = -100.0
+offset_right = 400.0
+grow_horizontal = 2
+grow_vertical = 0
+script = ExtResource("1_script")
+
+[node name="HBoxContainer" type="HBoxContainer" parent="."]
+layout_mode = 1
+anchors_preset = 15
+anchor_right = 1.0
+anchor_bottom = 1.0
+grow_horizontal = 2
+grow_vertical = 2
+theme_override_constants/separation = 4
+alignment = 1
+
+[node name="Slot1" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot2" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot3" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot4" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot5" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot6" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot7" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot8" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot9" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot10" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot11" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2
+
+[node name="Slot12" parent="HBoxContainer" instance=ExtResource("2_ability_button")]
+layout_mode = 2