docs: surface the runnable docs site from every entry point

[adamziel]

Summary

The runnable docs site at https://wordpress.github.io/php-toolkit/ shipped in #244 and the markdown sources behind it landed in #254. This PR makes it easy to find from every place a reader is likely to land.

What changed

github.com/WordPress/php-toolkit — Repo description and homepage URL are set via API to https://wordpress.github.io/php-toolkit/, so the sidebar on the repo page surfaces the docs link.

Root README.md — A "📚 Live, runnable docs" callout sits at the top, a per-component table replaces the bullet list (each row links to both the README and the matching reference page on the live site), and a "Building the docs site" subsection in the dev workflow points at bin/build-docs-bundle.sh + bin/serve-docs.py.

components/<Name>/README.md — All 18 component READMEs gain an idempotent banner immediately under the H1, deep-linking to that component's reference page. The banner is wrapped in HTML-comment markers so future URL/wording updates can be re-applied with one script:

<!-- docs-site-banner -->
> 📚 **Runnable examples:** [https://wordpress.github.io/php-toolkit/reference/zip.html](...)
> Open the page to edit each snippet in your browser and run it in WordPress Playground.
<!-- /docs-site-banner -->

components/<Name>/composer.json — Each per-component package (17 of them; ToolkitCodingStandards has no composer.json) gains:

• homepage → the matching reference page
• support: { issues, source, docs } → links visible on Packagist
• shared keywords: ["wordpress", "php-toolkit"]

The result: someone who lands on https://packagist.org/packages/wp-php-toolkit/zip sees a "Homepage" link to the runnable docs and a "Documentation" link in the support sidebar.

Root composer.json — The wp-php-toolkit/php-toolkit meta-package gets the same homepage + support block, plus a description that names the docs URL ("Browse runnable examples at https://wordpress.github.io/php-toolkit/").

examples/create-wp-site/README.md — Same docs-site banner under the H1 so readers in the examples folder don't miss the docs site.

AGENTS.md — A Docs site: pointer added next to the upstream/branch lines, with a one-liner that bin/_docs_components/<slug>.md is where the runnable examples live.

Test plan

• CI passes (no code changes; 87/87 snippets still match).
• After merge, https://github.com/WordPress/php-toolkit shows the homepage URL on the right sidebar.
• After Packagist re-sync (auto on next release, or manual via the package page), each wp-php-toolkit/* page surfaces the docs URL under "Homepage" and "Documentation".
• Component READMEs render the banner cleanly on github.com (HTML-comment markers stay invisible).

🤖 Generated with Claude Code