fix(cli): align find-docs skill with context7-cli rule guidance

[syf2211]

Summary

Align the generated find-docs skill with the companion context7-cli rule so ctx7 setup --claude --cli produces consistent guidance.

Motivation

Fixes #2860. The setup flow writes both find-docs/SKILL.md and ~/.claude/rules/context7.md, but they previously diverged:

• The skill recommended npm install -g ctx7@latest and bare ctx7 commands
• The skill examples used lowercase library slugs like nextjs and react
• The rule recommends npx ctx7@latest and official library punctuation (e.g. "Next.js" not "nextjs")

Because both files are regenerated on setup, the canonical skill source needed to match the rule.

Changes

• Update skills/find-docs/SKILL.md to use npx ctx7@latest as the canonical invocation style
• Add official library naming guidance matching rules/context7-cli.md
• Move global npm install -g to an optional secondary path
• Add regression tests in packages/cli/src/__tests__/find-docs-skill-alignment.test.ts

Tests

cd packages/cli && npx vitest run src/__tests__/find-docs-skill-alignment.test.ts
# 3 passed
cd packages/cli && npx vitest run
# 235 passed

Notes

Documentation-only change to the canonical skill template. Users receive the fix after the next skill re-download/update triggered by setup.

[enesgules]

Thanks for the contribution!