First pass at full refactor to 2.0 design

Restructures the game around the cyclical run loop from Game Design Doc V2:
5 waves = a cycle, 3 cycles = a phase, each phase ends in a boss.

- New TD.Gameplay.Waves: WaveGroup / PhaseDefinition / RunDefinition author the
  run as draggable weighted pools; RunState owns phase/cycle position, the drawn
  wave slots, and the per-slot enemy buff sets. WaveManager's flat wave array is
  gone -- it now only runs the encounter RunState points at.
- New TD.Gameplay.EnemyUpgrades: the post-wave enemy-buff vote, with public
  live-replicated ballots so the HUD can show who voted for what.
- Inter-wave flow is now strictly sequential: draft -> vote -> build, each stage
  ending early once every player has acted.
- Enemy abilities inverted from per-instance random rolls to deterministic,
  stacking per-wave-slot sets. Six cards ship: Split (reworked), Flight, Blink,
  No Bounty, Gold Theft, Double Up.
- Tower upgrades are a two-step tree: a draft pick unlocks a node, gold converts
  an already-placed tower in place.
- Boss encounters flag their enemies and drive a boss HP bar.
- Player cap reduced to 3 via MatchRules.MaxPlayers.
- GoldConfig is now keyed by global encounter number rather than wave index.

Compiles clean; NOT yet verified in-engine. Editor wiring still required --
see Docs/2.0_Setup_Checklist.md.

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

Assets/_Project/Scripts/Gameplay/EnemyAbilities/EnemySpawnContext.cs

@@ -0,0 +1,42 @@
+// Assets/_Project/Scripts/Gameplay/EnemyAbilities/EnemySpawnContext.cs
+namespace TD.Gameplay.EnemyAbilities
+{
+    /// <summary>
+    /// Mutable per-spawn copy of an enemy's stats, handed to each of its abilities before the
+    /// enemy is built so they can alter what it spawns as.
+    /// </summary>
+    /// <remarks>
+    /// <b>Why a context rather than more parameters.</b> Wave buffs like "grounded enemies become
+    /// flying" or "enemies spawn at half health" have to land <i>before</i>
+    /// <c>EnemyHealth.InitializeServer</c> and before the spawn position is computed (flyers are
+    /// raised by their flight height). Threading each new stat through <c>SpawnEnemy</c> as another
+    /// argument was already unwieldy at two; this keeps the signature flat and gives abilities one
+    /// obvious place to write.
+    ///
+    /// <para>Seeded from the <see cref="EnemyDefinition"/>, never written back to it — the
+    /// definition is a shared asset and a buff that mutated it would leak across waves, matches,
+    /// and (in the editor) sessions.</para>
+    /// </remarks>
+    public struct EnemySpawnContext
+    {
+        public float MaxHp;
+        public float MoveSpeed;
+        public bool  IsFlying;
+        public float FlightHeight;
+        public int   LivesCost;
+
+        /// <summary>Uniform transform scale relative to the prefab's authored scale.</summary>
+        public float VisualScale;
+
+        /// <summary>Seeds a context from an enemy definition's authored stats.</summary>
+        public static EnemySpawnContext FromDefinition(EnemyDefinition def) => new EnemySpawnContext
+        {
+            MaxHp        = def.MaxHp,
+            MoveSpeed    = def.MoveSpeed,
+            IsFlying     = def.IsFlying,
+            FlightHeight = def.FlightHeight,
+            LivesCost    = def.LivesCost,
+            VisualScale  = 1f,
+        };
+    }
+}