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/hyperframes-creative/references/story-spine.md

@@ -0,0 +1,37 @@
+# Story spine — value-first narrative doctrine
+
+Applies to the narrated, story-driven creation workflows — `/product-launch-video`, `/pr-to-video`, `/faceless-explainer`, `/website-to-video`, and `/general-video` when the piece tells a story. It does **not** apply to `/music-to-video` (the track drives the arc), `/motion-graphics` (no narration — motion is the message), `/embedded-captions` and `/talking-head-recut` (the footage's story is already fixed), or `/slideshow` (the presenter owns the story). Do not force these rules onto an exempt workflow.
+
+Each workflow's own story-design reference owns its archetypes, beat sequences, and frame vocabulary. This file owns three cross-workflow rules about **order** and **justification** — the reverse iceberg: lead with why it's valuable, not with what it is or how it was made.
+
+## 1. The hook speaks the viewer's language
+
+The first beat answers "why should I care" in **outcome language** — what the viewer gains, avoids, or finally understands. Subject-internal vocabulary is banned in the hook: file / function / API names for a code change; a feature list for a product; the source article's section headings for an explainer. Numbers are welcome only when they carry stakes ("40% faster cold starts"), never inventory ("23 files changed").
+
+## 2. Reverse iceberg — value before evidence
+
+The value claim (the brief's `message`) lands **by the second beat**. Everything after it is evidence in service of that claim — the diff, the mechanism, the feature demo, the site's screenshots. Implementation is the footnote of the story, not the spine.
+
+Self-check on the finished beat list:
+
+- Delete every evidence beat — the remaining beats must still state the value on their own.
+- Delete the value beats — if the video still seems to work, it was a feature tour / diff readout, not a story.
+
+Structure is value-first; the **voice** stays whatever the workflow prescribes (a PR video keeps its plain, no-hype developer voice — leading with value is an ordering decision, not a marketing register).
+
+## 3. The storyboard is a proposal, not a listing
+
+When Step 3 presents the plan (a checkpoint gate — `hyperframes-core/references/brief-contract.md` § 1):
+
+- Open by echoing the strategy line: **"This video tells [audience] that [message]."**
+- Present the frames as a markdown table, one row per frame:
+
+  | Frame            | Beat      | On screen                                               | Why                             |
+  | ---------------- | --------- | ------------------------------------------------------- | ------------------------------- |
+  | 01 — Not anymore | hook · 9s | States the old pain and resolves it in the same breath. | Lands the value claim in beat 1 |
+
+  **Why** is the frame's job in the story (from its `narrativeRole`), traced back to the message — a frame whose why cannot be traced to the message is a frame to cut, not to decorate.
+
+- Recommendations keep their receipts (brief-contract § 3): the archetype choice, the beat count, and any beat the user might question each state their basis.
+
+The proposal shape — echo line → frame table → style / duration footer → "approve or adjust" — is the cheapest place to iterate: a frame change here costs 30 seconds; the same change after build costs minutes.