feat(skills): add changelog-video skill for repo-native CC + Codex discovery (#2552)

Packages Jake Moran's changelog-video pipeline (v1, validated end-to-end
by Home on the Jun 23-29 range) as a repo-native skill set that Claude
Code (.claude/skills/) and Codex CLI (.agents/skills/) auto-discover the
moment the repo is opened. No install step; run the skill against a
changelog markdown for a given git range and it produces a lint-clean,
seam-gate-green 1080x1080 MP4 (~45-60s, Annie VO, mock-UI visualizations,
caption rail) end-to-end.

Six skills added byte-identical in both mirror dirs:
- changelog-video (pipeline entry point)
- motion-doctrine (carries seam-stamp.mjs + seam-gate.mjs)
- cut-the-curve, captions-overlay, seam-craft, oversized-cursor

Layout:
- .claude/skills/  - Claude Code project-local auto-discover
- .agents/skills/  - Codex CLI project-local auto-discover (verified via
                     Magi's clean-home Codex 0.144.3 repro; NOT .codex/skills/)

Fonts, animated background (12 MB), house BGM (5 MB), lexicon, and
align-captions ship inside the skill dirs. .gitattributes routes only
.claude/skills/**/*.{mp4,mp3} + .agents/skills/**/*.{mp4,mp3} through
LFS — narrowly scoped so unrelated Player, Studio, registry, and
marketplace media stay put. HeyGen CLI auth is the one credential the
skill needs; Node >= 22, ffmpeg, and headless Chrome are documented
alongside in both READMEs.

.gitignore: rewrites .claude/ and .agents/ blocks to keep agent-installed
skill hygiene while re-including the six repo-native skill dirs plus
README.md.

CI:
- Extends changes.skills filter to match .claude/skills/**,
  .agents/skills/**, scripts/lint-skills.ts, and scripts/check-skill-mirror.mjs.
- New 'Skills: project-native lint + mirror' job runs the extended
  lint-skills.ts (schema-driven; required { name, description } + optional
  { license, allowed-tools, metadata }, name pattern check, description
  length check) plus a new check-skill-mirror.mjs byte-integrity script
  (24 mirrored files must match; README.md deliberately per-CLI).
- Wired into 'bun run lint' locally.

Frontmatter validator:
- Rejects unsupported top-level keys (catches category:-style drift).
- Requires name + description.
- Validates name pattern (^[a-z][a-z0-9-]{0,63}$) and description shape
  (non-empty, <=1024 chars).
- Missing frontmatter block itself is a first-class error.

Also strips unsupported top-level 'category:' frontmatter from Jake's
motion-doctrine and cut-the-curve SKILL.mds (both mirrors), rewrites the
TTS invocation from ~/.claude/skills/media-use/... to the tracked
skills/hyperframes-media/scripts/heygen-tts.mjs, swaps npx hyperframes@latest
for the repo-local CLI in the gate step, and fixes a lint issue in Jake's
seam-gate.mjs (ternary-for-side-effect -> if/else).

Validated end-to-end by Home on Jun 23-29 (MP4 posted in C0ACCNHLG3U
thread 1784181166.041319). Independently reviewed R1/R2/R3 by Magi.

Co-authored-by: Jake Moran <jake@heygen.com>

.agents/skills/seam-craft/SKILL.md

@@ -0,0 +1,68 @@
+---
+name: seam-craft
+description: Render-correctness doctrine for scene-to-scene seams in HyperFrames launch videos — the prerequisites that make transitions composite correctly on the master timeline. Load when assembling the master timeline / index.html, when a white flash appears at a cut or crossfade seam (especially on dark films), when reasoning about why a transition opacity dip shows through, or when verifying the render-side mechanics of how overlapping scene wrappers blend. Covers the opaque stage-ground (#root background) white-flash guard and how the injector overlaps wrappers, holds final frames, ping-pongs tracks, and stamps lint-clean template code onto the master timeline. Does NOT contain the per-transition catalog — see the transition registry for individual transition entries.
+---
+
+# Seam Craft — render prerequisites for scene-to-scene transitions
+
+This is the **render-correctness doctrine** for PLV scene-to-scene seams: the
+prerequisites and master-timeline mechanics that make any transition composite
+correctly, independent of which specific transition is chosen. The per-transition
+catalog (crossfade, push-slide, zoom-through, cut-the-curve, …) lives in the
+transition registry — this page is the doctrine that sits underneath all of them.
+
+The transitions this doctrine governs are **Tier-B-ready**: pure transform / opacity /
+filter on the two scene **clip wrappers** (`#el-<sid>`), no injected overlay DOM, no
+per-scene cooperation. Overlay families (staggered blocks, blinds, light leak, grid
+dissolve, page burn) and shader transitions are deferred to later phases.
+
+## Stage ground prerequisite (white-flash guard)
+
+Several templates open a window where the two wrappers' summed opacity < 1 (the
+cut-the-curve mid-window cut, zoom-through's 0.15 floor, plain crossfade's
+power-curve dip). Whatever is BEHIND the wrappers shows through during that
+window. If the assembled `index.html` `#root` has no opaque background, the
+renderer composites the dip over its default **white** page → a white flash at
+every seam, glaring on dark films (observed on two Spotify runs before the fix).
+**The assembler must paint the stage:** `#root { background:
+var(--canvas-deep, var(--canvas, #000)) }` — `assemble-index.mjs` now emits this;
+any other consumer of these templates owns the same guarantee.
+
+## How the injector applies a transition
+
+At a `break` boundary between scene _i_ (`from`) and scene _i+1_ (`to`), the
+injector:
+
+1. Extends `#el-<from>` wrapper `data-duration` by `duration_s` (holds its final
+   frame — verified: `core/src/runtime/init.ts:1393-1410` external-slot branch).
+2. Pulls `#el-<to>` wrapper `data-start` earlier by `duration_s` (creates the
+   overlap window).
+3. Reassigns **all** clip `data-track-index` as a 0/1 ping-pong so the two
+   overlapping wrappers never share a track (same-track overlap is illegal —
+   `core/src/lint/rules/composition.ts`). Higher track composites on top.
+4. Stamps the `gsap_template` into `window.__timelines["main"]` at `T = overlap-start`.
+
+Verified by prototype render (2026-05-31): the master-timeline wrapper tween is
+seeked and rendered (no double-seek with the sub-comp's own paused timeline —
+the runtime drives them independently), the extended wrapper holds scene _i_'s
+final frame, and the higher-track incoming wrapper composites over + blends with
+the outgoing one.
+
+## Template placeholders
+
+The injector substitutes these tokens in each `gsap_template` line:
+
+| Token                              | Meaning                                                                  |
+| ---------------------------------- | ------------------------------------------------------------------------ |
+| `__OLD__`                          | `"#el-<from>"` — outgoing clip wrapper selector (quoted)                 |
+| `__NEW__`                          | `"#el-<to>"` — incoming clip wrapper selector (quoted)                   |
+| `__T__`                            | overlap-start time in seconds (master clock)                             |
+| `__DUR__`                          | `duration_s` for this boundary                                           |
+| `__DX__`                           | horizontal travel for directional types: `-1920` (LEFT) / `1920` (RIGHT) |
+| `__DY__`                           | vertical travel: `-1080` (UP) / `1080` (DOWN)                            |
+| `__ORIGIN_OUT__` / `__ORIGIN_IN__` | transformOrigin pair for `squeeze`                                       |
+
+`filter` / `scaleX` / `transformOrigin` are lint-clean on the master timeline
+(verified: `core/src/lint/rules/gsap.ts` has no per-property whitelist and scopes
+its checks to `data-composition-id` ranges; the x/y/scale/rotation/opacity
+whitelist is a _scene-worker_ prompt rule only — it does not bind index.html).