[DOCS] Document the automatic summary.md generation feature

Documentation Type

Missing documentation (feature not documented)

Documentation Location

https://code.claude.com/docs/en/settings

Section/Topic

Session Management

Current Documentation

_No response_

What's Wrong or Missing?

Claude Code automatically generates summary.md files for each session at:
~/.claude/projects/<project>/<session-id>/session-memory/summary.md

However, this feature is not documented in the official docs.

Suggested Improvement

### What needs documentation:

• How summary.md files are generated
• When they are updated
• What content do they contain
• The session-memory directory structure
• How to access/use these summaries

### Why this matters:

• Users are discovering these files, but don't understand their purpose
• Could be useful for reviewing past sessions
• Would help users build tools around this feature

Impact

Medium - Makes feature difficult to understand

Additional Context

_No response_