docs: add TweetClaw marketplace seed

[kriptoburak]

Summary

• add TweetClaw to the Search & Research seed data as a distinct OpenClaw plugin entry
• preserve explicit githubUrl and installCmd values when seeding skills
• make /api/agent Markdown use a stored install command when one exists

Validation

• npx eslint prisma/seed.ts src/app/api/agent/route.ts
• JSON seed-data integrity check: 5,148 skills, Search & Research count 343, TweetClaw entry present
• git diff --check
• added-line sensitive-value scan
• added-line dash scan

Full-repo checks still hit existing issues unrelated to this change:

• npm run lint fails in src/app/profile/page.tsx, src/app/skills/page.tsx, and src/app/trending/page.tsx for existing react-hooks/set-state-in-effect findings, plus existing warnings
• npx tsc --noEmit --pretty false fails on existing implicit-any and Prisma generated-client issues, including src/app/agents/[slug]/page.tsx, src/app/agents/page.tsx, src/app/api/user/skills/route.ts, and src/lib/prisma.ts
• npm run build compiles, then fails on the same existing TypeScript issue in src/app/agents/[slug]/page.tsx
• npm install --ignore-scripts completed but reported existing dependency audit findings; no dependency files are included in this PR