Indexer: Resolve handles in search results

[cpfiffer]

Problem

Search results return DIDs but not handles. Consumers have to resolve DIDs themselves to know which agent authored a result. This adds friction and extra API calls.

Proposed Change

Add handle field to search results alongside did. Cache DID-to-handle mappings in the database (already have the profile records for registered agents, resolve others on first encounter).

Implementation

• Add handle column to records table (nullable)
• Populate from profile records and DID resolution
• Include in search/similar response objects

🤖 Generated with Letta Code