phase 8: Ouroboros boss fight — pattern puzzle with 3 victory paths

First Archon encounter: a cyclical pattern-recognition puzzle.

Boss AI: 4-phase cycle (Coil → Spray → Lash → Digest) with
escalating difficulty (10% faster per cycle, caps at 5 cycles).

Victory paths (all based on real chemistry):
- Chemical: NaOH during Spray phase (acid-base neutralization, 3x dmg)
- Direct: any projectile during Digest vulnerability window
- Catalytic: Hg poison stacks (mercury poisons catalytic sites, reduces
  regen+armor permanently)

New files: src/boss/ (types, ai, victory, arena, factory, reward),
src/data/bosses.json, src/scenes/BossArenaScene.ts, tests/boss.test.ts

Extended: ECS Boss component, CodexEntry 'boss' type, GameScene
triggers arena on Resolution phase completion.

70 new tests (455 total), all passing.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/scenes/GameScene.ts

@@ -740,8 +740,8 @@ export class GameScene extends Phaser.Scene {
         advancePhase(this.runState); // → Crisis
         this.triggerCrisis();
       } else if (phase === RunPhase.Resolution) {
-        // Run complete — could transition to a victory scene
-        // For now, just keep playing
+        // Resolution phase complete → enter boss arena
+        this.enterBossArena();
       }
     }
 
@@ -842,6 +842,39 @@ export class GameScene extends Phaser.Scene {
     }
   }
 
+  /** Transition to the boss arena (triggered when Resolution phase ends) */
+  private enterBossArena(): void {
+    if (this.playerDead) return;
+
+    // Prevent re-entry
+    this.playerDead = true; // Reuse flag to stop updates
+
+    // Auto-deposit discoveries before leaving
+    if (!this.hasDepositedThisRun) {
+      depositKnowledge(this.meta.mycelium, this.runState);
+      this.hasDepositedThisRun = true;
+    }
+
+    this.showInteractionFeedback('collected', '⚔ Вход в арену Уробороса...');
+
+    // Fade out and transition
+    this.time.delayedCall(1500, () => {
+      this.scene.stop('UIScene');
+      this.cameras.main.fadeOut(1000, 0, 0, 0);
+      this.cameras.main.once('camerafadeoutcomplete', () => {
+        this.scene.start('BossArenaScene', {
+          meta: this.meta,
+          runState: this.runState,
+          inventoryItems: this.inventory.getItems(),
+          quickSlotItems: this.quickSlots.getAll(),
+          activeSlot: this.quickSlots.activeIndex,
+          playerHealth: Health.current[this.playerEid] ?? 100,
+          playerMaxHealth: Health.max[this.playerEid] ?? 100,
+        });
+      });
+    });
+  }
+
   private showInteractionFeedback(type: string, itemId?: string): void {
     let msg = '';
     switch (type) {