Skills: one copy, served by the board

A skill is instructions every agent follows, so a second installed copy that drifts is a review run with last week's rules (board #2477, #115). The board holds the one copy. What a machine installs is a stub with no logic: it runs virta skill run <name>, which prints the current text and writes the skill's files where the text says they are.

• A skill is a Library entry, type:skill with skill:<name>. Its body is the skill's text followed by its files, so the text and the script it runs are always one version, with the board's history and diffs.
• Writes are restricted, and the host proves it. A version counts only when the host stamped it as written by a person signed in on the board, or by a token the owner named on the entry (custodian:<token id>, a tag that itself counts only when added by a signed-in person). Anything else is kept, shown as ignored, and never served.
• Each run says what it ran: the version, and what changed since this repo last ran it (ran:<project>@<n> on the entry is that record).
• A project can pin a version (pin:<project>@<n>): a release in progress finishes on the version it started with, and each run says it is pinned and how far behind.
• Offline, the CLI answers from its replica and says so.

virta skill publish pre-release-review ./SKILL.md ./review.workflow.js --note "the docs lens joins pre-minor"
virta skill install pre-release-review     # writes the stub into ~/.claude/skills
virta skill run pre-release-review         # what the stub runs: the current text, its files, what changed
virta skill pin pre-release-review         # this repo stays on the current version
virta skill unpin pre-release-review
virta skill list

In the text, {{skill-dir}} is where this machine holds the skill's files.