feat(internal): Add custom claude code command seed-debug

[jsklan]

Description

Adds a custom Claude Code slash command /fern:seed-debug that provides an interactive debugging workflow for generator issues using the seed CLI.

Changes Made

• New slash command: Added .claude/commands/fern/seed-debug.md with comprehensive debugging workflow
• Permission settings: Added Bash(pnpm seed:local:*) to .claude/settings.json for auto-approval

The command supports:

• Debugging with predefined fixtures (--fixture) or custom Fern projects (--custom)
• Local generator builds (--local) or Docker-based execution
• Sequential-thinking MCP integration for systematic error analysis
• Automatic validation discovery from generated CI workflows

Testing

• Manual testing with various generator/fixture combinations
• Verified argument parsing (generator name, flags, description)
• Confirmed local config detection and user prompts

[github-actions]

🌱 Seed Test Selector

Select languages to run seed tests for:

• Python
• TypeScript
• Java
• Go
• Ruby
• C#
• PHP
• Swift
• Rust
• OpenAPI
• Postman

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How to use: Click the ⋯ menu above → "Edit" → check the boxes you want → click "Update comment". Tests will run automatically and snapshots will be committed to this PR.