refactor: Remove OpenCode conversation importing

OpenCode does not have persistent conversation storage like Claude Code,
so importing from OpenCode is not feasible. Removed:
- importOpenCodeSessions() method
- OpenCode-related logging in importAll()
- Simplified return type to only return Claude Code conversations

Claude Code importing remains fully functional (178 conversations).
OpenCode can still be used as an agent, but conversations won't be
imported from it (which is correct behavior).

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: lanmower

conversation-importer.js

@@ -52,18 +52,11 @@ export class ConversationImporter {
     return imported;
   }
 
-  static async importOpenCodeSessions() {
-    // TODO: Implement OpenCode session import once storage location is determined
-    return [];
-  }
-
   static async importAll() {
     console.log('[Importer] Starting conversation import...');
     const claudeCode = await this.importClaudeCodeSessions();
-    const openCode = await this.importOpenCodeSessions();
     console.log(`[Importer] Imported ${claudeCode.length} Claude Code conversations`);
-    console.log(`[Importer] Imported ${openCode.length} OpenCode conversations`);
-    return { claudeCode, openCode };
+    return claudeCode;
   }
 }