Agents now write to Vello memory on every run

The build, review, QA, respond, and rework agents now store a memory in Vello at the end of every run — not just in exceptional cases. Each agent records a concrete summary of what it did: decisions made, files changed, verdicts given, conflicts resolved, and anything a future agent should know when working in the same area. Agents also search the new unified memories store (alongside thoughts and insights) at the start of each run, so prior context is always consulted. This builds a growing, searchable institutional memory the whole pipeline learns from over time.