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/captions-overlay/SKILL.md

@@ -0,0 +1,81 @@
+---
+name: captions-overlay
+description: Overlay doctrine for the embedded-captions workflow — the caption MODEL (drop / rail / embed) and the rule that captions are an OVERLAY composited on top of the film, never a reserved bottom band you shift content up to avoid. Load when adding captions/subtitles to a talking-head or launch video, when deciding whether a phrase should be dropped, ride the verbatim rail, or be promoted to a scarce embedded climax, when laying out a composition that will carry captions (do NOT reserve a keep-out band), or when centering a composition on the true frame center under captions. Quotes the rail+embed model from embedded-captions and constraint #13 (captions overlay, keep-out band retired) from the product-launch-video scene agent. Applies ON TOP of embedded-captions.
+---
+
+# Captions Overlay Doctrine
+
+> **Overlay doctrine — supplements the upstream `embedded-captions` skill. Applies ON TOP of it; do not expect it folded into the upstream skill.**
+
+Two ideas combine here. First, the **caption model** — every spoken phrase is `drop`,
+`rail`, or `embed`, and embed is the scarce earned peak, not the default. Second, the
+**overlay law** — a caption line is composited ON TOP of the film as an overlay; it is
+NOT a reserved zone, so you never shift content up or leave a dead band to "make room"
+for it. The two reinforce each other: because captions ride as an overlay (the verbatim
+rail in front, the occasional embed behind the subject), the composition keeps its full
+frame and centers on the true vertical center.
+
+## The caption model — drop / rail / embed
+
+Every spoken phrase is one of three things (verbatim from `embedded-captions`):
+
+|           | What                                             | How it's shown                                                                                                                                                    |
+| --------- | ------------------------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| **drop**  | filler — um/uh, stutters, self-corrections       | not shown                                                                                                                                                         |
+| **rail**  | the default — ordinary spoken content (verbatim) | clean lower-third subtitle, **in front**, readable. A punch word can get an inline `emphasis` highlight (accent colour / active-word pop) — it stays on the rail. |
+| **embed** | a promoted peak — the headline beat              | one big word composited **behind the subject** (matte occlusion), designed entrance + exit                                                                        |
+
+**The rail carries most of the text; embed is the scarce, earned peak** — ≤1 per beat,
+never two adjacent/co-visible, spaced ≥ a beat apart. A short clip → usually one embed;
+a long explainer → ~one per section. Embedding every word is the common mistake.
+
+This is the **Standard** mode shape (rail = the verbatim lower-third; embed = the climax
+composited behind the subject). **Cinematic** mode drops the rail and makes everything
+embed-style — use it only for pure-cinematic asks, never for explainer / voiceover where
+the words must read.
+
+### Rail-first, embed-scarce (the load-bearing rules)
+
+Quoted from the `embedded-captions` non-negotiables:
+
+- **Rail-first for talking-head / explainer.** Don't embed the whole transcript — most
+  text is the rail; embed only peaks. Embedding everything is the default mistake.
+- **Embed is scarce + spaced.** ≤1 embed per sentence/beat, never two adjacent or
+  co-visible, ≥ a beat apart, at most one `apex`. climax = per-beat peak, **not** "the
+  single payoff of the entire clip."
+
+## The overlay law — captions are NOT a reserved band
+
+In a generated launch composition, when captions are enabled, finalize composites a
+**small, minimal word-by-word caption line** as an overlay layer ON TOP of the whole
+film (a single text line, bottom-centered, roughly the bottom ~5-8% of canvas height).
+It is an overlay, not a reserved zone (verbatim from constraint #13 of the
+product-launch-video scene agent):
+
+- **Center the composition on the TRUE vertical center — y = H / 2** (landscape 540,
+  portrait 960). Do not shift content up to "make room" for captions; a composition
+  centered at 0.42 × H with a dead lower band is the bug, not the fix.
+- Content may extend to the canvas bottom. Full-bleed subjects, rails, and backgrounds
+  all welcome.
+- **One soft courtesy rule:** avoid parking _critical small readable text_ (a URL line,
+  a legal line, a sub-caption) exactly in the bottom ~80px center span where the caption
+  line sits — the overlay would fight it. Large imagery / cards / ambient content under
+  the captions is fine; the caption skin is designed to read over content.
+- There is no machine keep-out gate (the old `captions.mjs keepout` check is retired).
+  Finalize snapshot QA judges caption-over-content legibility visually.
+
+**When captions are disabled:** identical positioning freedom — the overlay simply
+doesn't exist.
+
+## Why these two rules are one doctrine
+
+The model says the rail rides **in front** and an embed is a rare word composited
+**behind the subject** — both are layers added to footage that ships untouched. The
+overlay law says the caption line is a layer composited **on top** of the whole film,
+not a band carved out of the layout. So in both the captioning pipeline and the
+launch-video pipeline, captions are an overlay you add, not a zone you reserve:
+
+- Keep the full frame; center on true center; let content run to the edges.
+- Make the rail (or the small overlay caption line) carry the verbatim words.
+- Promote a word to an embed only at a genuine peak — scarce, spaced, never two at once.
+- Reserve nothing; judge legibility of captions-over-content visually, not by a keep-out gate.