Scale difficulty by run position; wipe towers at phase end

Follow-up pass on the 2.0 refactor, closing the gap between "waves are drawn
at random" and "difficulty still lives in the enemy assets".

- Enemy health is no longer authored per enemy type. New EnemyScalingConfig
  scales a per-zone HP *budget* by encounter number; per-enemy health is that
  budget divided by the wave's enemy count. Scaling the total rather than the
  per-enemy value keeps enemy count a texture knob (few tanks vs many swarmers)
  instead of a second, uncontrolled difficulty axis. EnemyDefinition.MaxHp
  becomes HpMultiplier, a deviation around 1.0. Speed stays archetype-only and
  unscaled -- escalating it compounds with health and invalidates tower balance
  mid-run.
- GoldConfig entries no longer reference a WaveDefinition. Payout is a property
  of run position, not of which wave got drawn: WaveGoldEntry ->
  EncounterGoldEntry, Waves -> Encounters, keyed by global encounter number.
  Its inspector labels elements "Encounter N" and projects cumulative earnings.
- The wave's voted buffs now show as icon badges in the top bar, read from the
  same RunState slot the spawn path uses so the display can't drift from what
  the enemies actually carry. Hover names the buff; unillustrated cards fall
  back to a lettered badge rather than vanishing.
- Clearing a phase's boss destroys every built tower, unrefunded. Queued build
  jobs still refund -- those towers were never delivered. Runs with the field
  empty, so the walkability churn doesn't hit the re-path scheduler.
- Fixed an RPC codegen break: [ClientRpc] requires a ClientRpc suffix, unlike
  the newer [Rpc(SendTo...)] style this file doesn't use.
- Setup checklist reordered into dependency order; it previously asked for a
  RunDefinition two sections before creating one.

Also carries the editor-side asset reorganisation into Definitions/RunDefinitions
and the sprite move into Enemy/Player draft icon folders.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assets/_Project/Scripts/Gameplay/EnemyDefinition.cs

@@ -12,6 +12,13 @@ namespace TD.Gameplay
     /// in project assets, only the asset reference (or its fields) crosses runtime code.
     /// Replace <see cref="EnemyPrefab"/> with a real mesh/animator when art is ready —
     /// no code changes required.
+    ///
+    /// <para><b>An enemy type is flavour, not a difficulty tier.</b> There is deliberately no
+    /// absolute health field: health comes from <see cref="EnemyScalingConfig"/> based on how far
+    /// into the run the encounter sits, and this asset only says how the type deviates from that
+    /// (<see cref="HpMultiplier"/>). Because waves are drawn at random from a phase pool, any
+    /// difficulty baked into the roster would be difficulty handed out by the luck of the draw.
+    /// Every type should be a viable occupant of any slot.</para>
     /// </remarks>
     [CreateAssetMenu(fileName = "EnemyDefinition", menuName = "TD/Enemy Definition", order = 3)]
     public class EnemyDefinition : ScriptableObject
@@ -21,10 +28,16 @@ namespace TD.Gameplay
         public string DisplayName;
 
         [Header("Stats")]
-        [Tooltip("Maximum hit points for this enemy type.")]
-        public float MaxHp = 100f;
+        [Tooltip("How tough this enemy is RELATIVE to its encounter's budget — not an absolute " +
+                 "hit-point value. 1.0 = exactly its share of the budget; 1.25 = a quarter " +
+                 "tougher than the slot calls for. Keep it near 1.0 and let the wave's enemy " +
+                 "count express tankiness (fewer enemies each get a bigger share).")]
+        [Min(0.01f)]
+        public float HpMultiplier = 1f;
 
-        [Tooltip("Movement speed in world units per second along the A* path.")]
+        [Tooltip("Movement speed in world units per second along the A* path. ABSOLUTE and " +
+                 "unscaled — speed is a fixed character trait, not a progression axis. See " +
+                 "EnemyScalingConfig for why.")]
         public float MoveSpeed = 3f;
 
         [Tooltip("When true this enemy flies: it paths on the baked terrain grid, ignoring " +