Add notification hook, directory CLAUDE.md scaffolding

- Wire Notification event in settings.json to new notify.sh hook
- notify.sh: Windows toast notifications via PowerShell balloon tip
- docs/CLAUDE.md: authoring standards for ADRs, TR registry, control manifest, engine reference
- design/CLAUDE.md: GDD directory guidance placeholder
- src/: scaffold with .gitkeep and CLAUDE.md authoring guide

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

.claude/hooks/notify.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+# Notification hook — fires when Claude Code sends a notification
+# Shows a Windows toast via PowerShell
+
+# Read notification JSON from stdin
+INPUT=$(cat)
+
+# Extract message — try jq first, fall back to grep
+if command -v jq &>/dev/null; then
+  MESSAGE=$(echo "$INPUT" | jq -r '.message // empty' 2>/dev/null)
+fi
+if [ -z "$MESSAGE" ]; then
+  MESSAGE=$(echo "$INPUT" | grep -oE '"message":"[^"]*"' | sed 's/"message":"//;s/"//')
+fi
+if [ -z "$MESSAGE" ]; then
+  MESSAGE="Claude Code needs your attention"
+fi
+
+# Sanitize message for PowerShell string embedding (escape single quotes)
+MESSAGE_SAFE=$(echo "$MESSAGE" | sed "s/'/''/g" | head -c 200)
+
+# Show Windows balloon tip notification (works on all Windows 10/11 without extra modules)
+powershell.exe -NonInteractive -WindowStyle Hidden -Command "
+  Add-Type -AssemblyName System.Windows.Forms
+  \$notify = New-Object System.Windows.Forms.NotifyIcon
+  \$notify.Icon = [System.Drawing.SystemIcons]::Information
+  \$notify.BalloonTipTitle = 'Claude Code'
+  \$notify.BalloonTipText = '$MESSAGE_SAFE'
+  \$notify.Visible = \$true
+  \$notify.ShowBalloonTip(5000)
+  Start-Sleep -Seconds 6
+  \$notify.Dispose()
+" 2>/dev/null &
+
+echo "Notification: $MESSAGE_SAFE"

.claude/settings.json

@@ -83,6 +83,18 @@
         ]
       }
     ],
+    "Notification": [
+      {
+        "matcher": "",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "bash .claude/hooks/notify.sh",
+            "timeout": 10
+          }
+        ]
+      }
+    ],
     "PreCompact": [
       {
         "matcher": "",