// Package skillpack is the SKILL.md-subscription battery: it lets an agent host
// subscribe to skill packages published as directories/git repos in the
// Anthropic "agent skills" format (a SKILL.md manifest plus optional bundled
// scripts and reference files) and activate them for a run with progressive
// disclosure.
//
// It is a THIRD, distinct concept from the two "skill" nouns already in the
// stack — do not conflate them:
//
//   - majordomo/skill  — a lightweight capability bundle (instructions + tools)
//     appended to an agent eagerly at construction.
//   - executus/skill   — a heavyweight persisted "saved agent" noun.
//   - executus/skillpack (this package) — an externally-authored, versioned,
//     on-demand-loaded instruction pack fetched from a Source and pinned by
//     content digest.
//
// Progressive disclosure is the reason this is not just a majordomo/skill:
// majordomo skills inject their whole instruction text into the system prompt
// up front, which does not scale to a catalog of large third-party packs. Here
// only each pack's name+description sits in the prompt permanently (the
// Catalog); the full body is loaded lazily when the model calls the single
// skill_use tool (see Activate).
//
// Design shape (each piece is nil-safe / host-agnostic, mirroring the other
// executus batteries):
//
//   - Manifest / ParseManifest — parse+validate a SKILL.md.
//   - Tree / Pack / LoadPack    — a fetched pack's files, content digest, and
//     parsed manifest.
//   - Source (Dir, Git)         — where packs come from; Fetch returns the file
//     tree and the source's resolved ref.
//   - Subscription + Store      — the persisted "this host tracks this pack at
//     this pinned digest" record; Memory is the zero-dep default.
//   - PackCache                 — content-addressed store of pinned pack trees
//     so activation never re-fetches; Memory default.
//   - Syncer                    — checks the tracked ref and records a PENDING
//     update; applying it is an explicit, separate re-pin (supply-chain guard —
//     upstream can never silently change what an agent runs).
//   - Catalog / Activate / Stage — turn a set of resolved packs into a
//     majordomo agent.Skill (catalog instructions + skill_use tool) and
//     materialize a pack's files for a sandbox.
//
// The host (e.g. mort) supplies policy: which sources are allowed, who may
// subscribe, and where staged files are mounted. This package supplies only the
// mechanism.
package skillpack

import "errors"

// ErrNotFound is returned when a subscription or cached pack lookup misses.
var ErrNotFound = errors.New("skillpack: not found")

// ErrNoManifest is returned when a fetched tree has no SKILL.md at its root.
var ErrNoManifest = errors.New("skillpack: tree has no SKILL.md")