feat: add web frontend rules and design quality hook

rules/web/patterns.md

@@ -0,0 +1,79 @@
+> This file extends [common/patterns.md](../common/patterns.md) with web-specific patterns.
+
+# Web Patterns
+
+## Component Composition
+
+### Compound Components
+
+Use compound components when related UI shares state and interaction semantics:
+
+```tsx
+<Tabs defaultValue="overview">
+  <Tabs.List>
+    <Tabs.Trigger value="overview">Overview</Tabs.Trigger>
+    <Tabs.Trigger value="settings">Settings</Tabs.Trigger>
+  </Tabs.List>
+  <Tabs.Content value="overview">...</Tabs.Content>
+  <Tabs.Content value="settings">...</Tabs.Content>
+</Tabs>
+```
+
+- Parent owns state
+- Children consume via context
+- Prefer this over prop drilling for complex widgets
+
+### Render Props / Slots
+
+- Use render props or slot patterns when behavior is shared but markup must vary
+- Keep keyboard handling, ARIA, and focus logic in the headless layer
+
+### Container / Presentational Split
+
+- Container components own data loading and side effects
+- Presentational components receive props and render UI
+- Presentational components should stay pure
+
+## State Management
+
+Treat these separately:
+
+| Concern | Tooling |
+|---------|---------|
+| Server state | TanStack Query, SWR, tRPC |
+| Client state | Zustand, Jotai, signals |
+| URL state | search params, route segments |
+| Form state | React Hook Form or equivalent |
+
+- Do not duplicate server state into client stores
+- Derive values instead of storing redundant computed state
+
+## URL As State
+
+Persist shareable state in the URL:
+- filters
+- sort order
+- pagination
+- active tab
+- search query
+
+## Data Fetching
+
+### Stale-While-Revalidate
+
+- Return cached data immediately
+- Revalidate in the background
+- Prefer existing libraries instead of rolling this by hand
+
+### Optimistic Updates
+
+- Snapshot current state
+- Apply optimistic update
+- Roll back on failure
+- Emit visible error feedback when rolling back
+
+### Parallel Loading
+
+- Fetch independent data in parallel
+- Avoid parent-child request waterfalls
+- Prefetch likely next routes or states when justified