Decision: Error on side of recording too much

## Context
After setting up Second Brain, Bob failed to save email auth work during the conversation. Henry called this out.

## Decision
**Save too much, not too little.** The cost of saving is cheap. The cost of forgetting is expensive.

## Updated Rules
- Save every 10-15 minutes during significant work
- Save before switching topics
- Save when something works (document what you did)
- Save when you learn anything
- Only skip: literal HEARTBEAT_OK with no action, pure small talk

## Why
- Embeddings cost pennies
- Lost context costs hours of repeated work
- Better to have too much searchable memory than gaps

## Action
Updated BRAIN.md with more aggressive save triggers.