feat(skills): hyperframes-registry skill (#261)

## What

New skill `hyperframes-registry` that teaches AI coding agents how to install and wire registry blocks and components into HyperFrames compositions.

### Skill structure
```
skills/hyperframes-registry/
  SKILL.md                          — triggers, overview, quick reference
  references/
    install-locations.md            — default paths, hyperframes.json config
    wiring-blocks.md                — iframe inclusion, data attributes, positioning
    wiring-components.md            — snippet merging (HTML, CSS, JS, timeline)
    discovery.md                    — manifest reading, item fields, available items table
    demo-html-pattern.md            — why components ship demo.html, structure conventions
  examples/
    add-block.md                    — worked example: data-chart block install + wiring
    add-component.md                — worked example: shimmer-sweep component install + wiring
```

## Why

Phase B of the catalog plan (PR 10). Without this skill, agents using `hyperframes add` have to guess how to wire installed items into compositions. The skill encodes the iframe/snippet patterns so agents get it right on the first attempt.

## How

- SKILL.md frontmatter triggers on: `hyperframes add`, "block", "component", `hyperframes.json`
- References cover every step: discovery, install, wiring blocks (iframe), wiring components (snippet merge), and the demo.html convention
- Two worked examples walk through complete install-to-preview workflows
- Updated CLAUDE.md skills table + trigger rules, README.md skills table, docs/packages/cli.mdx

## Test plan

- [x] `scripts/lint-skills.ts` passes (checked 4 skill files, no issues)
- [x] `oxfmt --check` passes on all markdown files
- [x] SKILL.md frontmatter has valid `name` and `description`
- [x] All reference links in SKILL.md resolve to existing files
- [x] CLAUDE.md, README.md, and docs CLI page updated with new skill

skills/hyperframes-registry/SKILL.md

@@ -0,0 +1,104 @@
+---
+name: hyperframes-registry
+description: Install and wire registry blocks and components into HyperFrames compositions. Use when running hyperframes add, installing a block or component, wiring an installed item into index.html, or working with hyperframes.json. Covers the add command, install locations, block iframe wiring, component snippet merging, and registry discovery.
+---
+
+# HyperFrames Registry
+
+The registry provides reusable blocks and components installable via `hyperframes add <name>`.
+
+- **Blocks** — standalone sub-compositions (own dimensions, duration, timeline). Included via `<iframe>` in a host composition.
+- **Components** — effect snippets (no own dimensions). Pasted directly into a host composition's HTML.
+
+## When to use this skill
+
+- User mentions `hyperframes add`, "block", "component", or `hyperframes.json`
+- Output from `hyperframes add` appears in the session (file paths, clipboard snippet)
+- You need to wire an installed item into an existing composition
+- You want to discover what's available in the registry
+
+## Quick reference
+
+```bash
+hyperframes add data-chart              # install a block
+hyperframes add grain-overlay           # install a component
+hyperframes add shimmer-sweep --dir .   # target a specific project
+hyperframes add data-chart --json       # machine-readable output
+hyperframes add data-chart --no-clipboard  # skip clipboard (CI/headless)
+```
+
+After install, the CLI prints which files were written and a snippet to paste into your host composition. The snippet is a starting point — you'll need to add `data-start` and `data-track-index` attributes when wiring blocks.
+
+Note: `hyperframes add` only works for blocks and components. For examples, use `hyperframes init <dir> --example <name>` instead.
+
+## Install locations
+
+Blocks install to `compositions/<name>.html` by default.
+Components install to `compositions/components/<name>.html` by default.
+
+These paths are configurable in `hyperframes.json`:
+
+```json
+{
+  "registry": "https://raw.githubusercontent.com/heygen-com/hyperframes/main/registry",
+  "paths": {
+    "blocks": "compositions",
+    "components": "compositions/components",
+    "assets": "assets"
+  }
+}
+```
+
+See [install-locations.md](./references/install-locations.md) for full details.
+
+## Wiring blocks
+
+Blocks are standalone compositions — include them via `data-composition-src` in your host `index.html`:
+
+```html
+<div
+  data-composition-id="data-chart"
+  data-composition-src="compositions/data-chart.html"
+  data-start="2"
+  data-duration="15"
+  data-track-index="1"
+  data-width="1920"
+  data-height="1080"
+></div>
+```
+
+Key attributes:
+
+- `data-composition-src` — path to the block HTML file
+- `data-composition-id` — must match the block's internal ID
+- `data-start` — when the block appears in the host timeline (seconds)
+- `data-duration` — how long the block plays
+- `data-width` / `data-height` — block canvas dimensions
+- `data-track-index` — layer ordering (higher = in front)
+
+See [wiring-blocks.md](./references/wiring-blocks.md) for full details.
+
+## Wiring components
+
+Components are snippets — paste their HTML into your composition's markup, their CSS into your style block, and their JS into your script (if any):
+
+1. Read the installed file (e.g., `compositions/components/grain-overlay.html`)
+2. Copy the HTML elements into your composition's `<div data-composition-id="...">`
+3. Copy the `<style>` block into your composition's styles
+4. Copy any `<script>` content into your composition's script (before your timeline code)
+5. If the component exposes GSAP timeline integration (see the comment block in the snippet), add those calls to your timeline
+
+See [wiring-components.md](./references/wiring-components.md) for full details.
+
+## Discovery
+
+Browse available items:
+
+```bash
+# Read the registry manifest
+curl -s https://raw.githubusercontent.com/heygen-com/hyperframes/main/registry/registry.json
+```
+
+Each item's `registry-item.json` contains: name, type, title, description, tags, dimensions (blocks only), duration (blocks only), and file list.
+
+See [discovery.md](./references/discovery.md) for details on filtering by type and tags.