Clay integration — embed code-editor in notebooks

[pbaille]

Summary

Minimal Clay integration: embed interactive noon code-editors in Clay notebook output.

Changes

Commit 1 — Decouple code-editor from global state

• code_editor.cljs: show-piano-roll? is now a prop instead of reading from noon.client.state
• doc.cljs: thin connected-code-editor wrapper injects the global toggle

Commit 2 — Clay integration

• noon.viz.clay (~30 lines): (editor source) returns kind/hiccup for Clay
• noon.widget (~45 lines): scans DOM for [data-noon-widget], mounts real code-editor
• Widget is part of the main client build (:entries in shadow module, no separate build)
• No init-fn — index.html and Clay pages call their entry points explicitly
• :clay alias in deps.edn (Clay 2.0.10 + Kindly)
• Test notebook: notebooks/clay_test.clj

Commit 3 — gitignore Clay output

What was NOT taken from widget-clay branch

• No separate shadow build
• No editor groups
• No auto-play / auto-eval
• No CDN URLs / deploy workflow changes
• No duplicated component — widget uses the real code-editor

Usage

(require '[noon.viz.clay :as nclay])
(nclay/editor "(play (tup s0 s1 s2 s3))")

Requires shadow-cljs watch client running locally.