feat: add x source research skill

[kriptoburak]

New Skill

Skill name: skills/x-source-research

Summary

Adds a source-backed X/Twitter research skill for customer research, social listening, competitor monitoring, content opportunity research, and campaign evidence workflows.

The skill covers query design, source packet capture, evidence confidence rules, synthesis steps, and compact output templates. This also updates the README, VERSIONS, and Claude plugin marketplace metadata for 45 skills and version 2.5.0.

Checklist

• name matches directory name exactly
• name follows naming rules (lowercase, hyphens, no --)
• description is 1-1024 chars with trigger phrases
• SKILL.md is under 500 lines
• No sensitive data or credentials
• Tested locally with AI agent

Validation run:

• ./validate-skills.sh
• ./validate-skills-official.sh
• git diff --check
• JSON and YAML frontmatter smoke checks