Add Twitter/X source packet guidance to research commands

[kriptoburak]

Summary

• Add optional public Twitter/X source packet guidance to competitor and market research commands
• Require source URLs and capture dates for social evidence, with unavailable state when evidence is missing
• Keep commands limited to analysis and monitoring ideas, not publishing, replies, DMs, or scheduling

Testing

• npx --yes markdown-link-check commands/competitor/deep.md commands/research/market.md --quiet
• git diff --check
• npm test
• npm run lint