feat(design): mandate full design toolchain on UI work via CLAUDE.md rule + hook

Add a tiered-by-scope "Design work — full toolchain" rule to the global
CLAUDE.md: trivial tweaks stay on /hotfix, building UI mobilizes ui-ux-pro-max,
frontend-design, Magic MCP, emil-design-eng, design-motion-principles, and
design-html; design systems start with design-consultation; reviews use
design-review + emil + motion audit. In doubt about scope, do not silently
skip the toolchain — ask or default to the Build tier.

Reinforce it with a design-toolchain-reminder UserPromptSubmit hook that
detects UI/design signals (broad FR+EN keyword set, \b-guarded against
substring false matches) and injects the tiered guidance into context. Soft
nudge, always exits 0, falls back to raw stdin when the hook JSON is missing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

settings.json

@@ -230,6 +230,16 @@
             "statusMessage": "Tracking caveman mode..."
           }
         ]
+      },
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash ~/.claude/hooks/design-toolchain-reminder.sh",
+            "timeout": 5,
+            "statusMessage": "Checking design signals..."
+          }
+        ]
       }
     ]
   },