[Feature Request] Session Checkpointing and Branching

Problem Statement:
When working on complex development tasks in Claude Code, users invest significant time getting Claude situated with project context, coding standards, and workflow understanding for an epic. However, as the context window fills up, this valuable context is lost when compaction or clearing becomes necessary. Regardless of the method used, Claude will not quite be at that same stage he was before - requiring reminders of requirements or corrections to get back on track. This degrades Claude's ability to iterate effectively on a set of related tasks.

Proposed Solution:
Leverage the existing session ID system to enable checkpointing and branching:
Within Claude Code REPL:

/checkpoint [optional-name] - Save current session state as a checkpoint
/list-checkpoints - Show available checkpoints with their session IDs

From command line:

claude-code --branch <session-id> - Start new session branched from the checkpointed session

Use Cases:

Epic Implementation: Get Claude situated with epic context and workflow, checkpoint that session, then branch new sessions for implementing individual tickets while maintaining that established understanding

SDK Workflows: Maintain established patterns and configurations across multiple related tasks (N8N workflows, API integrations, etc.)