feat: Introduce a comprehensive set of AI agent skills, agents, and workflows, along with new UI components and application structure.

.agent/skills/web-design-guidelines/SKILL.md

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+---
+name: web-design-guidelines
+description: Review UI code for Web Interface Guidelines compliance. Use when asked to "review my UI", "check accessibility", "audit design", "review UX", or "check my site against best practices".
+metadata:
+  author: vercel
+  version: "1.0.0"
+  argument-hint: <file-or-pattern>
+---
+
+# Web Interface Guidelines
+
+Review files for compliance with Web Interface Guidelines.
+
+## How It Works
+
+1. Fetch the latest guidelines from the source URL below
+2. Read the specified files (or prompt user for files/pattern)
+3. Check against all rules in the fetched guidelines
+4. Output findings in the terse `file:line` format
+
+## Guidelines Source
+
+Fetch fresh guidelines before each review:
+
+```
+https://raw.githubusercontent.com/vercel-labs/web-interface-guidelines/main/command.md
+```
+
+Use WebFetch to retrieve the latest rules. The fetched content contains all the rules and output format instructions.
+
+## Usage
+
+When a user provides a file or pattern argument:
+1. Fetch guidelines from the source URL above
+2. Read the specified files
+3. Apply all rules from the fetched guidelines
+4. Output findings using the format specified in the guidelines
+
+If no files specified, ask the user which files to review.
+
+---
+
+## Related Skills
+
+| Skill | When to Use |
+|-------|-------------|
+| **[frontend-design](../frontend-design/SKILL.md)** | Before coding - Learn design principles (color, typography, UX psychology) |
+| **web-design-guidelines** (this) | After coding - Audit for accessibility, performance, and best practices |
+
+## Design Workflow
+
+```
+1. DESIGN   → Read frontend-design principles
+2. CODE     → Implement the design
+3. AUDIT    → Run web-design-guidelines review ← YOU ARE HERE
+4. FIX      → Address findings from audit
+```