Publish the Registry Stack extension for Zed

Tracked by #399. Depends on #394 and #393.

## Outcome

Zed users can install a Registry Stack extension that attaches the shared project language server to Registry Stack YAML while retaining Zed's native YAML support.

Depends on the schema-driven baseline and shared Registry Stack language server.

## Requirements

- Register and launch the shared Registry Stack language server for the applicable YAML language.
- Preserve Zed's native YAML grammar, formatting, and yaml-language-server features.
- Activate project intelligence only within a detected Registry Stack project.
- Discover a compatible installed `registryctl` or language-server binary in accordance with Zed extension packaging rules.
- Provide an actionable status/error message for a missing binary or incompatible version.
- Support project-local settings without machine-specific committed paths.
- Publish through the Zed extension registry after local development-extension verification.

## Acceptance criteria

- [ ] Installing the extension in a clean supported Zed environment enables schema-driven editing and project navigation for a sample project.
- [ ] Normal YAML behavior remains available and unrelated YAML workspaces are unaffected.
- [ ] Language-server startup, restart, missing binary, and version mismatch paths are tested.
- [ ] Project-local schema settings and language-server settings do not require absolute paths.
- [ ] The extension performs no implicit live test, credential read, or network access during project analysis.
- [ ] macOS and supported Linux installation paths are documented and smoke-tested.
- [ ] Publication metadata, licensing, ownership, and release steps are documented.

## Non-goals

- Reimplementing authoring semantics in the Zed extension
- Shipping a divergent Zed-only language server
- Replacing Zed's YAML grammar or formatter

Commencez par lire la base pilotée par schéma dans #394 et le serveur de langage partagé dans #393, puis examinez les règles de packaging des extensions Zed. Vérifiez l’extension dans un environnement Zed propre en fonction des critères d’acceptation indiqués, notamment la préservation de YAML, la détection des projets, les erreurs des binaires, les paramètres, les chemins d’installation et la documentation de publication.

Rédigé par le modèle d'indexation à partir du texte de l'issue.