chore(skills): remove the unused skills-lock.json (#6503)

The lockfile was written by a third-party skills-installer CLI and rode
into the repo as a side effect of #5181. Nothing reads it: sync-skills.ts
treats `.agents/skills/<name>/SKILL.md` as canonical, and no script,
workflow, or Dockerfile references the file.

Its only real content was provenance for the three vendored skills, so
that moves to a `source:` frontmatter line on each SKILL.md. The
projector copies only `description`/`argument-hint`, leaving
`.claude/commands` and `.cursor/commands` byte-identical.

Author: waleedlatif1

.agents/skills/design-taste-frontend/SKILL.md

@@ -1,5 +1,6 @@
 ---
 name: design-taste-frontend
+source: https://github.com/leonxlnx/taste-skill — skills/taste-skill/SKILL.md
 description: Anti-slop frontend skill for landing pages, portfolios, and redesigns. The agent reads the brief, infers the right design direction, and ships interfaces that do not look templated. Real design systems when applicable, audit-first on redesigns, strict pre-flight check.
 ---
 

.agents/skills/emil-design-eng/SKILL.md

@@ -1,5 +1,6 @@
 ---
 name: emil-design-eng
+source: https://github.com/emilkowalski/skill — skills/emil-design-eng/SKILL.md
 description: This skill encodes Emil Kowalski's philosophy on UI polish, component design, animation decisions, and the invisible details that make software feel great.
 ---
 

.agents/skills/make-interfaces-feel-better/SKILL.md

@@ -1,5 +1,6 @@
 ---
 name: make-interfaces-feel-better
+source: https://github.com/jakubkrehel/make-interfaces-feel-better — skills/make-interfaces-feel-better/SKILL.md
 description: Design engineering principles for making interfaces feel polished. Use when building UI components, reviewing frontend code, implementing animations, hover states, shadows, borders, typography, micro-interactions, enter/exit animations, or any visual detail work. Triggers on UI polish, design details, "make it feel better", "feels off", stagger animations, border radius, optical alignment, font smoothing, tabular numbers, image outlines, box shadows.
 ---