feat(legal): add verify-citations skill

[narenkatakam]

Summary

• Adds a verify-citations skill to the legal plugin
• Fills a gap: the plugin reviews contracts, NDAs, and compliance, but has no workflow for verifying the authorities cited in a brief or memo before filing
• Goes beyond a pass/fail existence lookup — returns a citation-by-citation diagnostic with a specific failure mode per cite

What's new

1 new skill

Skill	What it covers
verify-citations	Five citation failure modes (fabricated, misattributed holding, wrong jurisdiction, hallucinated detail, coverage gap); a three-layer verification process (existence → holding → binding authority); confidence scoring; escalation criteria

README updated

• Added verify-citations to the Skills table

Why this matters

Documented AI-hallucinated-citation sanctions crossed 1,200+ cases by early 2026 (Mata v. Avianca, Whiting v. City of Athens, Lacey v. State Farm). The dangerous failures are not fabricated cases — those get caught — but real cases cited for holdings they never made, which pass a simple existence check. This skill separates "doesn't exist" from "doesn't support the claim" from "can't be verified," and tells the reviewer exactly what to fix.

What's NOT changed

• .claude-plugin/plugin.json, .mcp.json, CONNECTORS.md, LICENSE — untouched
• All existing skills — untouched (purely additive)

Design decisions

• Diagnostic, not binary. Existing citation tools return PASS/FAIL on existence. This skill classifies how a citation fails, because "exists" does not mean "supports your argument" and "not found" does not mean "fabricated."
• Honest about its limits. The skill states plainly that it supports — and does not replace — the filer's independent verification duty (e.g., Fed. R. Civ. P. 11), and degrades gracefully when no research connector is available rather than guessing.
• Consistent style. Follows the existing pattern: YAML frontmatter (name, description, argument-hint), connectors banner, legal-advice disclaimer, Usage / What I Need From You / Output template, and a Tips section — matching compliance-check and legal-risk-assessment.

Files changed

New files (1):

• legal/skills/verify-citations/SKILL.md

Modified files (1):

• legal/README.md — added verify-citations to the Skills table

Test plan

• Skill has valid YAML frontmatter (name, description, argument-hint)
• Follows existing style (connectors banner, legal-advice disclaimer, Usage/Output template, Tips)
• README Skills table updated consistently
• No existing content modified or removed (purely additive)