fix(css): collapse ad slots initially to prevent layout shift

- Slots start with max-height:0, opacity:0, margin:0 (no visual space)
- Only expand when AdSense confirms filled status
- Use transition for smooth appearance
- Prevents layout shift when unfilled slots are hidden
- Combined with larger rootMargin (1000px) slots are pre-loaded
  before entering viewport, eliminating visible collapse

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.claude/settings.local.json

@@ -4,7 +4,11 @@
       "Bash(mkdir:*)",
       "mcp__serena__activate_project",
       "mcp__serena__find_symbol",
-      "Bash(ssh:*)"
+      "Bash(ssh:*)",
+      "Bash(php:*)",
+      "mcp__playwright__browser_console_messages",
+      "mcp__playwright__browser_evaluate",
+      "mcp__playwright__browser_navigate"
     ]
   }
 }