ENHANCEMENT: Enable cross-session memory with memory frontmatter field

[ali5ter]

Motivation

The agent currently acknowledges it cannot store persistent state:

Track these mentally throughout the conversation (you cannot store persistent state, but reference these conceptually)

This means every session starts cold. The agent cannot:

• Remember the user's preferred default level
• Track recurring warning signs across sessions
• Recall previous "explain-back" outcomes
• Build a picture of which problem areas the user struggles with

The Claude Code subagent framework now supports persistent memory via the memory frontmatter field (user, project, or local scopes).

Proposed Change

Add to coach.md frontmatter:

memory: user

user scope (~/.claude/agent-memory/coach/) is appropriate because:

• The coaching relationship is personal, not project-specific
• The user may use this agent across many different projects
• Warning sign observations and level preferences should travel with the user

The agent system prompt should be updated with guidance on:

• What to remember (preferred level, recurring struggle areas, warning sign history)
• What not to remember (ephemeral session state, specific code from past sessions)
• When to read and write memory within a session