feat(media-use): resolve engine + BGM/SFX/image/icon providers (#1683)

* feat(media-use): core infrastructure — manifest, cache, adopt, probe

Foundation for media-use — the media resolution layer for HyperFrames.

- manifest.mjs: JSONL read/write/find for .media/manifest.jsonl
- index-gen.mjs: regenerate agent-readable index.md from manifest
- cache.mjs: content-addressed global cache at ~/.media/ (SHA-256, sentinel)
- freeze.mjs: download URL or copy local file to .media/
- probe.mjs: extract duration/dimensions via ffprobe
- adopt.mjs: scan assets/ directory, register existing files with metadata
- 19 passing tests (manifest round-trip, cache, promote, index generation)

* fix(media-use): oxfmt formatting + cap freeze download size

Format adopt/cache/probe/manifest.test (CI oxfmt --check gate).
Cap freezeUrl downloads at 256MB so a hostile/runaway URL can't fill
the disk (addresses CodeQL #670: network data written to file).

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

* feat(media-use): resolve engine + all providers + brand from frame.md

- resolve.mjs: cheapest-first cascade
- BGM/SFX via heygen --headers, Image/Icon via heygen asset search
- Brand tokens from frame.md / design.md (local, no API)
- SKILL.md: full agent docs + hyperframes.dev/design redirect
- Router skill + workflow skill references

* fix(media-use): oxfmt formatting for resolve + providers

Format brand/heygen-search/providers/sfx providers + resolve.mjs
(CI oxfmt --check gate).

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

* fix(media-use): align providers with the real heygen CLI surface (v0.1.6)

Verified live against the official Go `heygen` CLI v0.1.6 with a valid key:

- Caller attribution: pass `--headers 'X-HeyGen-Client-Source: media-use'`
  (the allowlisted flag the CLI added for media-use in v0.1.6). The old
  `--x-source media-use` was never a real flag and broke every call.
- Command is `asset search` (the `list` leaf was dropped in v0.1.6), not
  `asset search list`.
- `--min-score` is sent server-side: honored by `audio sounds list`, but the
  `asset search` backend rejects it and returns no score field, so only the
  audio providers pass it (image/icon don't).
- Drop hardcoded `ext` so resolve.mjs derives it from the URL: catalog icons
  are .png (not .svg), some BGM is .wav (not .mp3).

Also: surface CLI/auth failures on stderr instead of swallowing them as
'no results', carry icon width/height through, and document the heygen CLI
install + >= v0.1.6 requirement.

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

---------

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

skills/pr-to-video/SKILL.md

@@ -3,6 +3,8 @@ name: pr-to-video
 description: "turn a GitHub pull request (a PR URL like github.com/<owner>/<repo>/pull/<N>, an <owner>/<repo>#<N> ref, or 'this PR' in a checked-out repo) into a code-change explainer video, up to ~3 min (sweet spot 30-90s) — changelog, feature reveal, fix, or refactor walkthrough, rendered from the diff / commits / files. The input is a CODE CHANGE read via the gh CLI; there is no website capture. Use this skill for a GitHub PR. Do not use it for a product launch/promo (use /product-launch-video), a tour of a real website (use /website-to-video), a topic explainer with no PR (use /faceless-explainer), captions on existing footage (use /embedded-captions), or a short unnarrated motion graphic (use /motion-graphics). If the intent is unclear, route through /hyperframes first."
 ---
 
+> **media-use**: Before sourcing audio/images, call `/media-use` to resolve BGM/SFX/images from the HeyGen catalog. Run `--adopt` first to register existing assets. See `/media-use` skill.
+
 # PR to HyperFrames
 
 Use this skill to ingest a GitHub pull request, understand the change, plan a code-change explainer, and build it frame by frame in HyperFrames. The input is a **code change** (read via `gh`), not a website — there is **no capture step and no real assets** beyond the contributors' avatars.