chore(skills): move upstream skills to the CLI global store, keep authored tier

Retroactive provenance: the 10 pi-era skill snapshots were byte-identical
to upstream. Canonical installs now live in ~/.agents/skills tracked by
~/.agents/.skill-lock.json (mattpocock/skills x38 after grilling removal,
find-skills from vercel-labs/skills).

Repo tier is authored overrides only: clear all 10 tracked upstream
snapshots; omp loads the store directly through the agents provider
(skills.enableAgentsUser, default on). grilling returns as a real
directory — extracted from the store (CLI + lockfile pruned) so Frank can
customize it without skills update resurrecting a twin.

Docs: skill-store-wiring.md (+index). Pre-cutover snapshot of the old
tracked dirs at /tmp/agent-skills-snap-20261018.

omp-docs/tools/vercel-labs-skills/index.md

@@ -14,5 +14,6 @@ Complete list of 68+ supported coding agents, their --agent flags, and installat
 | [related-links.md](related-links.md) | reference | Links to the Agent Skills specification, skills directory, integration guide,... |
 | [skill-discovery.md](skill-discovery.md) | reference | How the skills CLI discovers SKILL.md files in repositories — flat layout, ca... |
 | [skill-format.md](skill-format.md) | reference | The required frontmatter fields, optional fields, internal skills, and struct... |
+| [skill-store-wiring.md](skill-store-wiring.md) | reference | How omp's agent/skills directory is symlinked into the skills CLI global store, and where lockfile provenance lives. |
 | [source-formats.md](source-formats.md) | reference | All accepted source formats for skills add and use — GitHub shorthand, full U... |