feat: replace browser dialogs with in-game naming screen + notifications

Remove prompt() and alert() calls that broke game immersion. Add:
- Pokemon-style naming screen with character grid + direct typing
- Canvas-rendered notification toasts (with fade-out animation)
- Both render on top of workshop AND world mode canvases
- Workshop keyboard handler yields to naming screen when active

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

js/world/worldRenderer.js

@@ -6,7 +6,7 @@ import {
 import { worldState } from './worldState.js';
 import { getMap, getInteraction, getNPC, getExit, isWall } from './maps.js';
 import { updateMovement } from './worldInput.js';
-import { drawBackpack, getGadgets } from './inventory.js';
+import { drawBackpack, getGadgets, drawNamingScreen, drawNotification } from './inventory.js';
 
 let canvas = null;
 let ctx = null;
@@ -144,6 +144,12 @@ export function renderWorld(timestamp) {
     if (worldState.mode === 'inventory') {
         drawBackpack(ctx, canvas.width, canvas.height);
     }
+
+    // === Layer 7: Naming screen (on top of everything including backpack) ===
+    drawNamingScreen(ctx, canvas.width, canvas.height);
+
+    // === Layer 8: Notification toast ===
+    drawNotification(ctx, canvas.width);
 }
 
 function drawHUD(map) {