[codex] expose remote plugin share URL (#27890)

## Summary

- expose the remote plugin detail endpoint's `share_url` as nullable
`PluginDetail.shareUrl`
- preserve existing `PluginSummary.shareContext` behavior for local and
workspace sharing flows
- regenerate the app-server TypeScript and JSON schema fixtures

## Why

The remote plugin detail response already includes a canonical
`share_url`, but that value was not surfaced by `plugin/read` for global
plugins. Global plugins intentionally have no `shareContext`, so using
that model for the URL would change the semantics consumed by the
existing share modal.

## User impact

Codex clients can use `PluginDetail.shareUrl` for a remote plugin's
copy-link action, including when the plugin is disabled by an
administrator, without changing existing share-modal or ownership
behavior.

## Validation

- `cargo test -p codex-app-server
plugin_read_includes_share_url_for_admin_disabled_remote_plugin`
- `cargo test -p codex-app-server-protocol
typescript_schema_fixtures_match_generated`
- `cargo test -p codex-app-server-protocol
json_schema_fixtures_match_generated`
- `cargo fmt --all`

codex-rs/app-server/src/request_processors/plugins.rs

@@ -1070,6 +1070,7 @@ impl PluginRequestProcessor {
                         interface: outcome.plugin.interface.map(local_plugin_interface_to_info),
                         keywords: outcome.plugin.keywords,
                     },
+                    share_url: None,
                     description: outcome.plugin.description,
                     skills: plugin_skills_to_info(
                         &visible_skills,
@@ -2081,6 +2082,7 @@ fn remote_plugin_detail_to_info(
         marketplace_name: detail.marketplace_name,
         marketplace_path: None,
         summary: remote_plugin_summary_to_info(detail.summary),
+        share_url: detail.share_url,
         description: detail.description,
         skills: detail
             .skills