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/theme/wow_style.tres

@@ -0,0 +1,12 @@
+[gd_resource type="Theme" load_steps=2 format=3]
+
+[ext_resource type="FontFile" uid="uid://dh88edx2pf6ax" path="res://assets/fonts/Kurland.ttf" id="1_font"]
+
+[resource]
+default_font = ExtResource("1_font")
+default_font_size = 16
+
+; WoW-style color palette
+; Gold accent color for highlights and borders
+; Dark backgrounds with semi-transparency
+; Health colors: green -> yellow -> red gradient