Slice 1: combat readability + HUD declutter (DR-038)

Four playtest do-now wins:
- Enemy health bars: pooled world-space Canvas, on-damage-sticky + fade,
  always-on <25% HP (CombatFeedbackSystem; no new replication).
- Telegraph fix: new baked client-safe EnemyTelegraph sizes the danger-cone ramp
  per enemy (0->1 ending at impact, fixes the Charger plateau); windup 18->22;
  a windup scale-pulse.
- Build-mode toggle: BuildPaletteState.PaletteOpen hides the palette by default,
  Tab / gamepad-Y toggles, with a discovery chip (HudSystem/BuildSendSystem).
- Charger committed-lunge tell: [GhostEnabledBit] IsLunging derived once/tick from
  LungeState (the Dead idiom); the danger cone persists through the lunge.

345/345 EditMode (+3 IsLunging derive tests); Play-validated: ghost-hash change
did not break the handshake, bake correct (telegraph on all enemies, IsLunging
baked-disabled on the Charger, replicated to client), no runtime errors.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Assets/_Project/Scripts/Client/Building/BuildSendSystem.cs

@@ -91,8 +91,16 @@ namespace ProjectM.Client
 
             HandleBuildMode(connection);
 
-            // Hotkey fallback (suppressed while the palette build mode is active).
+            // --- Build-palette toggle (Tab / gamepad Y): Slice 1 HUD declutter — the palette is hidden by default ---
             var keyboard = UnityEngine.InputSystem.Keyboard.current;
+            var gamepad = UnityEngine.InputSystem.Gamepad.current;
+            bool togglePressed =
+                (keyboard != null && keyboard.tabKey.wasPressedThisFrame) ||
+                (gamepad != null && gamepad.buttonNorth.wasPressedThisFrame);
+            if (togglePressed && !PauseMenuController.Open)
+                BuildPaletteState.TogglePalette();
+
+            // Hotkey fallback (suppressed while the palette build mode is active).
             if (keyboard != null && !BuildPaletteState.Active)
             {
                 if (keyboard.leftBracketKey.wasPressedThisFrame)