feat(skills): mode-first briefs, value-first storyboards, and destination defaults across creation workflows (#2058)

* feat(skills): add brief contract — interaction modes + shared intake fields across workflows

New hyperframes-core/references/brief-contract.md, the shared intake
contract every creation workflow now runs its brief against:

- §1 interaction mode: collaborative (default) vs autonomous, ongoing
  vs one-time signals, mode set once and carried forward, and a gate
  taxonomy (preference / checkpoint / quality / routing) — autonomous
  skips waiting, never verification
- §2 field registry: destination→aspect derivation (feed → 1:1,
  Shorts/TikTok → 9:16, else 16:9), message, angle, length, audience,
  language, narration — each workflow binds fields as ask or state
- §3 question rules: one round with one question per asked field
  (native question UI mandatory when available, recommended option
  first with a receipt), never drop a question as inferable, and a
  mode legend advertised in the intro text instead of asked

Wired into the surfaces:

- hyperframes router: detect mode at entry, derive aspect from
  destination instead of stating 16:9
- product-launch-video / pr-to-video / faceless-explainer: ask/state
  binding tables at Step 0; Step 3/6 checkpoint-gate branches
  (autonomous posts a heads-up with a preview hint before render)
- website-to-video: local mode definition now defers to the contract
- music-to-video, general-video, embedded-captions, talking-head-recut,
  slideshow, motion-graphics: mode semantics wired per gate type
- storyboard-format: new optional 'mode' frontmatter key
- pr-to-video: length tier is a ceiling, not a floor — a one-headline
  PR recommends inside the 30–90s sweet spot regardless of diff size

* feat(skills): story spine + mode-first brief across creation workflows

Story — the reverse-iceberg feedback:

- New hyperframes-creative/references/story-spine.md, three rules for
  the narrated workflows: the hook speaks the viewer's outcome
  language, the value claim lands by beat 2 (implementation is the
  footnote of the story, not the spine), and the storyboard is
  presented as a proposal — 'This video tells [audience] that
  [message]' plus a per-frame why: drawn from narrativeRole
- pr-to-video: feature-reveal reordered promise-first (impact leads,
  diff/mechanism follow as evidence); hooks ban file/function names;
  fix-explainer, refactor-walkthrough, changelog unchanged
- product-launch-video / faceless-explainer hook rules aligned to the
  spine; website-to-video's beat summary gains the echo line + why:;
  general-video points at the spine from its plan step

Brief — hardened after live-test drift:

- Mode is now the first question (Collaborative recommended vs
  Autonomous), its own round, skipped when the request carries a
  signal; autonomous asks nothing further until one final
  preview-or-render question before render
- Step 0 rewritten as a literal two-round question script in each
  shot-sequence workflow (website-to-video's editorial register,
  channel-agnostic); brief-contract.md §3 reduced to invariants so the
  procedure lives in exactly one place

* feat(skills): split type minimums by viewing context

typography.md: full-screen viewing keeps body 20px / headline 60px;
in-feed destinations (X / LinkedIn / Instagram — brief-contract's
destination field) scale to body >=32px, headline >=90px, data labels
>=24px. First-pass values, to be calibrated against real renders.

* feat(skills): storyboard proposal as a table + credits close by default

- story-spine § 3: the proposal presents frames as a markdown table
  (frame · beat · on screen · why) instead of dense paragraphs; the
  three shot-sequence workflows and website-to-video's beat summary
  reference the same shape
- pr-to-video: the credits close is now the default ending — every PR
  video ends on a contributors frame (committers by commit count, 1-6
  avatars), with no taste judgment; the only skip is when no avatar
  was fetched, and the user can cut the frame in the proposal

* fix(skills): address review nits on the brief/story contracts

- embedded-captions: the identity procedure now states both sides of the
  preference gate inline (user picks; autonomous picks with a stated why)
- website-to-video step-2-brief: note that its mode section is the
  workflow's application of brief-contract.md, not a second definition
- brief-contract: resuming a project reads mode from STORYBOARD.md
  frontmatter — a recorded mode counts as set, closing the write-only gap

* docs(skills): add a non-code receipts example to the brief contract

Review nit (jrusso1020, #2058): the receipts example in § 3 was
PR-video-shaped only. A destination-shaped example joins it so the rule
reads as workflow-neutral.

skills/music-to-video/SKILL.md

@@ -9,7 +9,7 @@ description: "Turn a music track (an audio file, a video to pull audio from, or
 
 Use this skill to turn a **music track** into a beat-synced HyperFrames video. You analyze the track once, lay out the frames, fill in a per-frame plan, and build each frame as a composition. The input is a music track plus optional user images or videos — there is **no narration and no website capture**. Typography and templates are the floor (a complete video needs zero assets); any media the user supplies is cut in on the same beat grid.
 
-You are the **orchestrator**. Work in `videos/<project>/`. Run the steps in order and pass each **Gate** before moving on. Two steps need the user: **Step 3** (plan approval) and **Step 6** (render approval). Do every step yourself except **Step 4**, where you dispatch **one sub-agent per frame**. Keep design and motion rules out of this file — they live in `references/` and the `frame-worker` sub-agent.
+You are the **orchestrator**. Work in `videos/<project>/`. Run the steps in order and pass each **Gate** before moving on. Two steps need the user: **Step 3** (plan approval) and **Step 6** (render approval) — both are checkpoint gates per `../hyperframes-core/references/brief-contract.md` (read it before Step 0): in autonomous mode, post the summary as a heads-up and proceed instead of waiting. Do every step yourself except **Step 4**, where you dispatch **one sub-agent per frame**. Keep design and motion rules out of this file — they live in `references/` and the `frame-worker` sub-agent.
 
 `SKILL_DIR` = this skill directory. `PROJECT_DIR` = `videos/<project-name>/`.
 
@@ -91,9 +91,9 @@ node <SKILL_DIR>/scripts/validate-plan.mjs --storyboard "$PROJECT_DIR/STORYBOARD
   --audiomap "$PROJECT_DIR/audiomap.json" --templates <SKILL_DIR>/references/templates
 ```
 
-Fix every `✗` (hard errors: duration mismatch, frames not tiling the track, a missing `src`); warnings are best-effort. Then show the user a frame-by-frame summary and iterate until they approve.
+Fix every `✗` (hard errors: duration mismatch, frames not tiling the track, a missing `src`); warnings are best-effort. Then show the user a frame-by-frame summary and iterate until they approve. In autonomous mode this is a checkpoint gate: post the summary as a heads-up and proceed (the `validate-plan.mjs` pass is a quality gate and still blocks).
 
-**Gate:** `frame.md` is a verbatim preset copy; `validate-plan.mjs` exits 0; the user approved the plan.
+**Gate:** `frame.md` is a verbatim preset copy; `validate-plan.mjs` exits 0; the user approved the plan (autonomous: the summary was posted as a heads-up).
 
 ---
 
@@ -149,13 +149,13 @@ Run the CLI on the **assembled project** — that's the correct unit (the per-fr
 ( cd "$PROJECT_DIR" && npx hyperframes lint . && npx hyperframes validate . && npx hyperframes inspect . )
 ```
 
-Inspect at `t=0`, each frame start, the strongest DROP / SURGE, every `hard_stops[].t`, and the final frame. On failure, make the **cheapest safe fix** yourself: edit the offending `compositions/frames/NN-*.html`. Never change duration or audio timing to hide a sync issue. Once the gates pass, pause for user review, then render only on approval:
+Inspect at `t=0`, each frame start, the strongest DROP / SURGE, every `hard_stops[].t`, and the final frame. On failure, make the **cheapest safe fix** yourself: edit the offending `compositions/frames/NN-*.html`. Never change duration or audio timing to hide a sync issue. Once the gates pass, pause for user review, then render only on approval (autonomous mode: ask the one kept question — "preview first, or render?" — then deliver the MP4 with the contact sheet):
 
 ```bash
 ( cd "$PROJECT_DIR" && npx hyperframes render . --skill=music-to-video -q draft -o renders/video.mp4 --fps 30 )
 ```
 
-**Gate:** `lint` / `validate` / `inspect` passed; the user approved; `renders/video.mp4` exists with audio, duration == `audiomap.audio.duration_sec`. The final reply states the MP4 path and duration.
+**Gate:** `lint` / `validate` / `inspect` passed; the user approved (autonomous: checks passed and the delivery includes the contact sheet); `renders/video.mp4` exists with audio, duration == `audiomap.audio.duration_sec`. The final reply states the MP4 path and duration.
 
 ---