feat: Expose plugin versions and gate plugin sharing (#22397)

- Adds localVersion to plugin summaries and remoteVersion to share
context, including generated API schemas.
- Hydrates local and remote plugin versions from manifests and remote
release metadata.
- Adds default-on plugin_sharing gate for shared-with-me listing and
plugin/share/save, with disabled-path errors
    and focused coverage.

codex-rs/features/src/lib.rs

@@ -188,6 +188,8 @@ pub enum Feature {
     ComputerUse,
     /// Temporary internal-only flag for PS-backed remote plugin catalog development.
     RemotePlugin,
+    /// Enable remote plugin sharing flows.
+    PluginSharing,
     /// Show the startup prompt for migrating external agent config into Codex.
     ExternalMigration,
     /// Allow the model to invoke the built-in image generation tool.
@@ -1007,6 +1009,12 @@ pub const FEATURES: &[FeatureSpec] = &[
         stage: Stage::UnderDevelopment,
         default_enabled: false,
     },
+    FeatureSpec {
+        id: Feature::PluginSharing,
+        key: "plugin_sharing",
+        stage: Stage::Stable,
+        default_enabled: true,
+    },
     FeatureSpec {
         id: Feature::ExternalMigration,
         key: "external_migration",