chore: add vercel skills

.agents/skills/vercel-composition-patterns/README.md

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+# React Composition Patterns
+
+A structured repository for React composition patterns that scale. These
+patterns help avoid boolean prop proliferation by using compound components,
+lifting state, and composing internals.
+
+## Structure
+
+- `rules/` - Individual rule files (one per rule)
+  - `_sections.md` - Section metadata (titles, impacts, descriptions)
+  - `_template.md` - Template for creating new rules
+  - `area-description.md` - Individual rule files
+- `metadata.json` - Document metadata (version, organization, abstract)
+- **`AGENTS.md`** - Compiled output (generated)
+
+## Rules
+
+### Component Architecture (CRITICAL)
+
+- `architecture-avoid-boolean-props.md` - Don't add boolean props to customize
+  behavior
+- `architecture-compound-components.md` - Structure as compound components with
+  shared context
+
+### State Management (HIGH)
+
+- `state-lift-state.md` - Lift state into provider components
+- `state-context-interface.md` - Define clear context interfaces
+  (state/actions/meta)
+- `state-decouple-implementation.md` - Decouple state management from UI
+
+### Implementation Patterns (MEDIUM)
+
+- `patterns-children-over-render-props.md` - Prefer children over renderX props
+- `patterns-explicit-variants.md` - Create explicit component variants
+
+## Core Principles
+
+1. **Composition over configuration** — Instead of adding props, let consumers
+   compose
+2. **Lift your state** — State in providers, not trapped in components
+3. **Compose your internals** — Subcomponents access context, not props
+4. **Explicit variants** — Create ThreadComposer, EditComposer, not Composer
+   with isThread
+
+## Creating a New Rule
+
+1. Copy `rules/_template.md` to `rules/area-description.md`
+2. Choose the appropriate area prefix:
+   - `architecture-` for Component Architecture
+   - `state-` for State Management
+   - `patterns-` for Implementation Patterns
+3. Fill in the frontmatter and content
+4. Ensure you have clear examples with explanations
+
+## Impact Levels
+
+- `CRITICAL` - Foundational patterns, prevents unmaintainable code
+- `HIGH` - Significant maintainability improvements
+- `MEDIUM` - Good practices for cleaner code

.agents/skills/vercel-composition-patterns/SKILL.md

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+---
+name: vercel-composition-patterns
+description:
+  React composition patterns that scale. Use when refactoring components with
+  boolean prop proliferation, building flexible component libraries, or
+  designing reusable APIs. Triggers on tasks involving compound components,
+  render props, context providers, or component architecture. Includes React 19
+  API changes.
+license: MIT
+metadata:
+  author: vercel
+  version: '1.0.0'
+---
+
+# React Composition Patterns
+
+Composition patterns for building flexible, maintainable React components. Avoid
+boolean prop proliferation by using compound components, lifting state, and
+composing internals. These patterns make codebases easier for both humans and AI
+agents to work with as they scale.
+
+## When to Apply
+
+Reference these guidelines when:
+
+- Refactoring components with many boolean props
+- Building reusable component libraries
+- Designing flexible component APIs
+- Reviewing component architecture
+- Working with compound components or context providers
+
+## Rule Categories by Priority
+
+| Priority | Category                | Impact | Prefix          |
+| -------- | ----------------------- | ------ | --------------- |
+| 1        | Component Architecture  | HIGH   | `architecture-` |
+| 2        | State Management        | MEDIUM | `state-`        |
+| 3        | Implementation Patterns | MEDIUM | `patterns-`     |
+| 4        | React 19 APIs           | MEDIUM | `react19-`      |
+
+## Quick Reference
+
+### 1. Component Architecture (HIGH)
+
+- `architecture-avoid-boolean-props` - Don't add boolean props to customize
+  behavior; use composition
+- `architecture-compound-components` - Structure complex components with shared
+  context
+
+### 2. State Management (MEDIUM)
+
+- `state-decouple-implementation` - Provider is the only place that knows how
+  state is managed
+- `state-context-interface` - Define generic interface with state, actions, meta
+  for dependency injection
+- `state-lift-state` - Move state into provider components for sibling access
+
+### 3. Implementation Patterns (MEDIUM)
+
+- `patterns-explicit-variants` - Create explicit variant components instead of
+  boolean modes
+- `patterns-children-over-render-props` - Use children for composition instead
+  of renderX props
+
+### 4. React 19 APIs (MEDIUM)
+
+> **⚠️ React 19+ only.** Skip this section if using React 18 or earlier.
+
+- `react19-no-forwardref` - Don't use `forwardRef`; use `use()` instead of `useContext()`
+
+## How to Use
+
+Read individual rule files for detailed explanations and code examples:
+
+```
+rules/architecture-avoid-boolean-props.md
+rules/state-context-interface.md
+```
+
+Each rule file contains:
+
+- Brief explanation of why it matters
+- Incorrect code example with explanation
+- Correct code example with explanation
+- Additional context and references
+
+## Full Compiled Document
+
+For the complete guide with all rules expanded: `AGENTS.md`

.agents/skills/vercel-composition-patterns/metadata.json

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+{
+  "version": "1.0.0",
+  "organization": "Engineering",
+  "date": "January 2026",
+  "abstract": "Composition patterns for building flexible, maintainable React components. Avoid boolean prop proliferation by using compound components, lifting state, and composing internals. These patterns make codebases easier for both humans and AI agents to work with as they scale.",
+  "references": [
+    "https://react.dev",
+    "https://react.dev/learn/passing-data-deeply-with-context",
+    "https://react.dev/reference/react/use"
+  ]
+}

.agents/skills/vercel-composition-patterns/rules/_sections.md

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+# Sections
+
+This file defines all sections, their ordering, impact levels, and descriptions.
+The section ID (in parentheses) is the filename prefix used to group rules.
+
+---
+
+## 1. Component Architecture (architecture)
+
+**Impact:** HIGH  
+**Description:** Fundamental patterns for structuring components to avoid prop
+proliferation and enable flexible composition.
+
+## 2. State Management (state)
+
+**Impact:** MEDIUM  
+**Description:** Patterns for lifting state and managing shared context across
+composed components.
+
+## 3. Implementation Patterns (patterns)
+
+**Impact:** MEDIUM  
+**Description:** Specific techniques for implementing compound components and
+context providers.
+
+## 4. React 19 APIs (react19)
+
+**Impact:** MEDIUM  
+**Description:** React 19+ only. Don't use `forwardRef`; use `use()` instead of `useContext()`.

.agents/skills/vercel-composition-patterns/rules/_template.md

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+---
+title: Rule Title Here
+impact: MEDIUM
+impactDescription: brief description of impact
+tags: composition, components
+---
+
+## Rule Title Here
+
+Brief explanation of the rule and why it matters.
+
+**Incorrect:**
+
+```tsx
+// Bad code example
+```
+
+**Correct:**
+
+```tsx
+// Good code example
+```
+
+Reference: [Link](https://example.com)

.agents/skills/vercel-composition-patterns/rules/architecture-avoid-boolean-props.md

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+---
+title: Avoid Boolean Prop Proliferation
+impact: CRITICAL
+impactDescription: prevents unmaintainable component variants
+tags: composition, props, architecture
+---
+
+## Avoid Boolean Prop Proliferation
+
+Don't add boolean props like `isThread`, `isEditing`, `isDMThread` to customize
+component behavior. Each boolean doubles possible states and creates
+unmaintainable conditional logic. Use composition instead.
+
+**Incorrect (boolean props create exponential complexity):**
+
+```tsx
+function Composer({
+  onSubmit,
+  isThread,
+  channelId,
+  isDMThread,
+  dmId,
+  isEditing,
+  isForwarding,
+}: Props) {
+  return (
+    <form>
+      <Header />
+      <Input />
+      {isDMThread ? (
+        <AlsoSendToDMField id={dmId} />
+      ) : isThread ? (
+        <AlsoSendToChannelField id={channelId} />
+      ) : null}
+      {isEditing ? (
+        <EditActions />
+      ) : isForwarding ? (
+        <ForwardActions />
+      ) : (
+        <DefaultActions />
+      )}
+      <Footer onSubmit={onSubmit} />
+    </form>
+  )
+}
+```
+
+**Correct (composition eliminates conditionals):**
+
+```tsx
+// Channel composer
+function ChannelComposer() {
+  return (
+    <Composer.Frame>
+      <Composer.Header />
+      <Composer.Input />
+      <Composer.Footer>
+        <Composer.Attachments />
+        <Composer.Formatting />
+        <Composer.Emojis />
+        <Composer.Submit />
+      </Composer.Footer>
+    </Composer.Frame>
+  )
+}
+
+// Thread composer - adds "also send to channel" field
+function ThreadComposer({ channelId }: { channelId: string }) {
+  return (
+    <Composer.Frame>
+      <Composer.Header />
+      <Composer.Input />
+      <AlsoSendToChannelField id={channelId} />
+      <Composer.Footer>
+        <Composer.Formatting />
+        <Composer.Emojis />
+        <Composer.Submit />
+      </Composer.Footer>
+    </Composer.Frame>
+  )
+}
+
+// Edit composer - different footer actions
+function EditComposer() {
+  return (
+    <Composer.Frame>
+      <Composer.Input />
+      <Composer.Footer>
+        <Composer.Formatting />
+        <Composer.Emojis />
+        <Composer.CancelEdit />
+        <Composer.SaveEdit />
+      </Composer.Footer>
+    </Composer.Frame>
+  )
+}
+```
+
+Each variant is explicit about what it renders. We can share internals without
+sharing a single monolithic parent.