feature/Add automatic LLM-assisted memory update prompting

[DJJones66]

Summary

Adds automatic memory update prompting for BrainDrive starter-pack changes. On startup, the gateway now detects when the current starter pack targets a newer memory pack version, generates a migration plan, applies safe updates, defers risky/customized changes, writes an owner-readable report, and updates memory state so the migration does not rerun every startup.

What Changed

• Added memory update engine for starter-pack manifest generation, planning, apply, backup, report, and migration state tracking.
• Added optional LLM planning with deterministic fallback.
• Added startup gateway integration and memory update API endpoints.
• Added client-side update notice/report display after completed updates.
• Disabled legacy starter-skill bootstrap during gateway startup so the update engine owns starter-pack skill creation/reporting.
• Added regression and integration tests for update status, planning, apply, reporting, deferred files, repeat-startup prevention, and incomplete LLM plan normalization.

Validation

• npm --prefix builds/typescript run test -- memory/update-prompting.test.ts
• npm --prefix builds/typescript run test -- gateway/auth-routes.integration.test.ts
• npm --prefix builds/typescript run build