feat: add Claude Code marketplace support

[manav148]

Summary

• Add .claude/skills/ with prd and ralph skills for Claude Code marketplace
• Add .claude-plugin/ with marketplace.json and plugin.json for plugin discovery
• Update README with Claude Code installation instructions

Available Skills

• /prd - Generate Product Requirements Documents
• /ralph - Convert PRDs to prd.json format

Installation

/plugin marketplace add snarktank/ralph
/plugin install ralph-skills@ralph-marketplace

Or use directly with:

claude --plugin-dir /path/to/ralph

Test plan

• Verified skills are discoverable with claude --plugin-dir . -p "List available skills"
• Verified skill descriptions are correct
• Tested prd skill invocation

🤖 Generated with Claude Code

[snarktank]

@manav148 Thank you for working on this. The reason I left the skills out is because there's not agreement on where these should be stored right now. Amp puts skills in ~/.config/amp/skills so your implementation won't work for Amp users. Can you update this so it works for as many agents as possible - not just CC?

[manav148]

Thanks for the feedback! I believe this implementation already works for both Amp and Claude Code users. Let me clarify:

For Amp users (unchanged workflow):

• Skills remain in skills/prd/ and skills/ralph/ exactly as before
• Users copy to ~/.config/amp/skills/ as documented in the README
• The only change is adding user-invocable: true to the YAML frontmatter, which Amp safely ignores (unknown YAML fields are skipped)

For Claude Code users (new capability):

• .claude-plugin/ points to the existing skills/ directory
• No duplicate files - same skills work for both tools

What this PR does NOT do:

• Does not move skills to .claude/skills/ or any Claude-specific location
• Does not break the existing Amp installation workflow
• Does not require any changes for current Amp users

The skills/ directory is the single source of truth for both tools. Would you like me to clarify anything in the README or make other adjustments?

[snarktank]

This looks good to merge but there are merge conflicts. Could you rebase on main and resolve the conflicts? Then I'll merge it.

[manav148]

can you take a look and merge before we get more conflicts?