Auto-memory write template should emit lifecycle frontmatter fields (status / superseded_by / last-reviewed)

Context

Claude Code auto-memory writes memory files with frontmatter containing
name, description, type. We've extended our memory governance with
three lifecycle fields that drive automated retirement sweeps. The
upstream auto-memory template doesn't know about them, so they only get
written when an agent remembers to add them by hand.

Desired behaviour

The auto-memory write template should emit:

---
name: <memory name>
description: <one-line hint>
type: <user|feedback|project|reference>
status: active
superseded_by: null
last-reviewed: <ISO date of write>
---

Why

• Removes the "agent forgot the field" failure mode entirely
• Makes lifecycle queryable from day one rather than after a back-fill sweep
• Forward-compatible: consumers without the new fields see them as inert frontmatter

Workaround in the meantime

A periodic sweep parses missing fields with documented defaults, so the
absence is non-blocking. But the sweep is a band-aid — fixing the template
removes the gap.