… in CI

- Remove vendor/, build/, assets/build/ from git tracking (.gitignore already excluded them); they are now generated on the fly in CI and locally
- Rework build-assets.yml into 'Playground Build': builds JS assets, installs production composer deps, creates plugin zip via wp-scripts plugin-zip, uploads it as a workflow artifact
- Playground PR link now installs the built artifact through playground.wordpress.net/plugin-proxy.php instead of the raw branch zip, so PRs are testable without committing build output

The npm build script chains 'npm run makepot' which requires WP-CLI,
not available on the CI runner (exit 127: wp not found). The Playground
test zip does not need a regenerated .pot file, so run only the
wp-scripts build and admin JS build steps.

playground.wordpress.net/plugin-proxy.php rejects non-allowlisted orgs,
so the artifact-proxy approach cannot work for this repo. Instead the
workflow now pushes the built zip to a dedicated playground-builds
branch (kept at a single orphan commit) and links Playground to the
raw.githubusercontent.com URL, which serves the required CORS headers.
A commit-sha cache-buster in the URL ensures each PR push gets a link
to that exact build.

- release.yml: on GitHub Release publish, verify tag matches plugin
  header and readme stable tag, build JS assets + pot file, install
  production composer deps, deploy to wp.org SVN via
  10up/action-wordpress-plugin-deploy and attach the zip to the
  release; manual dispatch supports dry-run
- asset-update.yml: sync .wordpress-org assets and readme.txt to the
  SVN assets dir on push to master via
  10up/action-wordpress-plugin-asset-update
- .distignore: authoritative exclude list for the deployed package
- .wordpress-org/: banners, icons and screenshots tracked in repo as
  the source of truth for wp.org store assets
- Remove legacy .svnignore (replaced by .distignore)
- Ship uninstall.php in plugin zip (was missing from package.json files)

The original untracking commit lost its deletions during a rebase;
this restores the intended state. vendor/, build/ and assets/build/
are generated by CI and local builds, and are already in .gitignore.

Co-Authored-By: Claude Fable 5 <[email protected]>