chore(skills): sync .claude/skills mirror with skill_templates

[satyaborg]

Summary

.claude/skills/ (this repo's own dogfooded install of its skills) has drifted from the canonical src/kensa/skill_templates/. All four skills present differ, and kensa-diagnose is missing from .claude/skills/ entirely.

Evidence

$ diff -q .claude/skills/kensa-setup/SKILL.md src/kensa/skill_templates/kensa-setup/SKILL.md
Files .claude/skills/kensa-setup/SKILL.md and src/kensa/skill_templates/kensa-setup/SKILL.md differ
$ diff -q .claude/skills/kensa-evals/SKILL.md src/kensa/skill_templates/kensa-evals/SKILL.md
Files .claude/skills/kensa-evals/SKILL.md and src/kensa/skill_templates/kensa-evals/SKILL.md differ
$ diff -q .claude/skills/kensa-generate/SKILL.md src/kensa/skill_templates/kensa-generate/SKILL.md
Files .claude/skills/kensa-generate/SKILL.md and src/kensa/skill_templates/kensa-generate/SKILL.md differ
$ diff -q .claude/skills/kensa-inspect/SKILL.md src/kensa/skill_templates/kensa-inspect/SKILL.md
Files .claude/skills/kensa-inspect/SKILL.md and src/kensa/skill_templates/kensa-inspect/SKILL.md differ
$ ls .claude/skills/
kensa-evals kensa-generate kensa-inspect kensa-setup   # no kensa-diagnose

Location

.claude/skills/ vs src/kensa/skill_templates/

Fix

Symlink .claude/skills/<name> to src/kensa/skill_templates/<name> instead of maintaining duplicate copies, and add the missing kensa-diagnose entry.

Why it matters

Duplicate copies silently diverge. This repo dogfoods its own skills through .claude/skills/, so a stale mirror means local development runs against outdated instructions while the shipped templates move on.