Add claude-skills and claude-session-skills marketplaces - #340

Two new marketplace entries under ## Marketplaces:

• claude-skills — 7 standalone skills: Gemma 4 31B prompting reference, iPhone Mirroring automation, layered explanations, Higgsfield generation guide, Gemini audio transcription, a 5-layout social carousel designer, and a pre-production testing gauntlet.
• claude-session-skills — session-handoff + persist-session, a paired session-continuity/memory system.

Both are real, working plugin marketplaces (.claude-plugin/marketplace.json), each plugin validated with claude plugin validate and installed end-to-end from the published repo before listing here.

🤖 Generated with Claude Code