docs(skill): shader/audio/render/snapshot guidance from regression evidence

Adds decision guidance and conventions the 8-site regression test exposed as
blind spots — agents had the capability but never reached for it.

step-1-capture:
- Clarify capture goes into <project-dir>/capture/ so capture artifacts stay
  isolated from later build files (SCRIPT/STORYBOARD/DESIGN/compositions/)
- 7/8 regression tests already did this; codify as the convention

step-4-storyboard:
- Add "When to pick which" decision table for shader vs CSS vs hard cut
  transitions. Shader transitions were available but used in 0/8 tests —
  every test defaulted to CSS. The table frames shaders as "reveals, reaction
  shots, brand moments" vs CSS as "connective tissue"
- Update technique count (10 → 11)

step-6-build:
- Mid-scene activity table gets a new row for audio-reactive logo/CTA
  animation (bass pulse, treble glow). Audio-reactive was used in 0/8 tests
  despite narration being present in all of them

step-7-validate:
- Snapshot section: explicit "use hyperframes snapshot, don't roll custom"
  with the default naming pattern spelled out. Stripe's run used custom
  ffmpeg naming (beat-6-cta-at-20.5s.png) instead of frame-XX-at-Ys.png
- New render section: require --output renders/<project>.mp4 so final MP4s
  have predictable names. Without this, 7/8 tests produced wildly different
  filenames (preview.mp4, cal_2026-04-19_20-29-21.mp4, basecamp.mp4, etc.)

techniques.md:
- New technique #11: Audio-Reactive Animation. Covers the sampling pattern
  (per-frame tl.call, not single tween), when to use (music/dramatic VO
  videos), intensity ranges (3-5% for text/logos, 10-30% for backgrounds),
  and anti-patterns (equalizer bars, waveforms, strobing). Cross-references
  skills/hyperframes/references/audio-reactive.md for the full API

Made-with: Cursor

skills/website-to-hyperframes/references/step-1-capture.md

@@ -2,10 +2,18 @@
 
 ## Run the capture
 
+Create a project directory for your video, then capture the website into a `capture/` subfolder within it:
+
 ```bash
-npx hyperframes capture <URL> -o captures/<project-name>
+npx hyperframes capture <URL> -o <project-dir>/capture
 ```
 
+Example: `npx hyperframes capture https://stripe.com -o videos/stripe-launch/capture`
+
+Keeping the capture artifacts (`screenshots/`, `assets/`, `extracted/`, `AGENTS.md`, `CLAUDE.md`) in a dedicated `capture/` subfolder keeps them isolated from the later build files (`SCRIPT.md`, `STORYBOARD.md`, `DESIGN.md`, `compositions/`, `index.html`, `narration.wav`, `transcript.json`, `renders/`, `snapshots/`), which all live at `<project-dir>/` root.
+
+For exploratory captures that aren't becoming a video yet, `-o captures/<name>` at the repo root is fine — the isolation convention only matters when you're building a video on top of the capture.
+
 No API keys required. The capture extracts design tokens, screenshots, fonts, and assets with DOM-context descriptions automatically.
 
 **Optional:** Set `GEMINI_API_KEY` (or `GOOGLE_API_KEY`) in a `.env` file at the repo root for richer AI-powered image descriptions via Gemini 3.1 Flash Lite vision (~$0.001/image).