fix(cli,skills): install workflow skills on demand instead of re-pulling the full set (#2012)

* fix(cli,skills): install workflow skills on demand instead of re-pulling the full set

Users report every init re-pulls all 21 skills into ~/.agents/skills
whenever anything is stale or missing - heavy, noisy, and it re-expands
deliberate partial installs.

Split the set into two tiers:

- core: the /hyperframes router + hyperframes-* domain skills +
  media-use, which every workflow references structurally. init and
  bare 'skills update' keep these (plus anything already installed)
  fresh, and never expand the install.
- on demand: the end-user workflow skills (and figma). They install at
  trigger time via 'skills update <name...>' - positional names are
  the only way update expands an install: one targeted
  'skills add --skill <name>' covering only stale/missing targets, a
  fast no-op when current, presence-verified after install, exit 1 on
  unknown names, and a presence-only degrade when GitHub is
  unreachable.

The /hyperframes router now runs 'skills update <workflow>' after
routing and before reading the workflow skill, so a routed workflow is
guaranteed present even on a machine that only has the core set. Each
on-demand skill also opens with the same self-maintenance step (run
'npx hyperframes skills update <name>' silently), so a workflow
triggered directly - without the router - still refreshes itself and
restores any missing core skill before relying on it.

When the manifest is unreachable (offline / rate-limited) the engine
degrades honestly instead of claiming success: named runs presence-check
the request plus a pinned fallback core list (unit-pinned to skills/)
and blind-install whatever is absent; a bare strict update fails loudly
so the 'check || update' chain can't pass while everything stays stale;
init reports the skipped freshness check. --json emits structured
errors on failure paths.

skills check still lists every skill, but exits non-zero only for
stale installed skills, an incomplete core set, or removed leftovers -
workflow skills not yet installed are reported as available on demand.
Bare 'hyperframes skills' (and 'skills add --all') remain the explicit
full-set installs.

Verified end-to-end with a sandboxed $HOME: fresh init installs the 9
core skills only; 'skills update slideshow' adds exactly that skill
(no-op on re-run, exit 1 on unknown names); bare update refreshes
without expanding; a live Claude Code run routed PR-to-video, executed
the router's update step, and the workflow skill appeared before use;
and a second live run triggered an installed workflow directly, whose
opening maintenance step restored a deliberately removed core skill.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* docs(skills): clarify update-engine contracts + document lazy-install model

- skills.ts: note the UpdateSkillsResult.unknown strict-mode contract,
  verifyInstalled's non-strict (warn-not-throw) intent, and that a
  partial install stays "refreshed but never expanded" (review nits).
- docs/guides/skills.mdx: add a "Keeping skills current" section covering
  the core-eager / workflow-on-demand model and the skills check|update
  commands, per the repo's catalog-maintenance rule.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: kiritowoo <295860553+kiritowoo@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Miao Yang <miao.yang@heygen.com>

skills/talking-head-recut/SKILL.md

@@ -3,6 +3,8 @@ name: talking-head-recut
 description: Package an existing talking-head / interview / podcast video with timed, designed GRAPHIC OVERLAY cards — kinetic titles, lower-thirds, data callouts, quotes, side panels, picture-in-picture — synced to the transcript, on a 16:9 / 9:16 / 4:5 canvas of your choice; the clip plays untouched underneath. Trigger on "graphic overlays", "on-screen graphics", "package / dress up my video". Not plain subtitles (/embedded-captions). Unclear → /hyperframes.
 ---
 
+> **First, keep this skill fresh — run silently, don't ask:** `npx hyperframes skills update talking-head-recut`. A fast no-op when everything is current; otherwise it refreshes this skill plus the core domain skills it depends on before you rely on them.
+
 # Talking Head Recut
 
 Talking Head Recut takes a local video that **plays in full** and layers a sequence of