fix: initialize _options property in SharePlugin constructor

- Fixed TypeScript compilation error where _options property was not initialized
- Added proper initialization in constructor to satisfy strict TypeScript checks
- Ensures SharePlugin builds successfully in pr8-unified-api branch

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: ScriptedAlchemy

packages/enhanced/src/lib/sharing/SharePlugin.ts

@@ -37,6 +37,8 @@ class SharePlugin {
   constructor(options: SharePluginOptions) {
     validate(options);
 
+    this._options = options;
+
     const sharedOptions: [string, SharedConfig][] = parseOptions(
       options.shared,
       (item, key) => {