[FEATURE] Clone/duplicate conversation to try different approaches

Problem

When working on a complex task, I often want to try a different approach from a specific point without losing my current conversation thread. Currently:

• Starting a new session loses all the context I've built up
• There's no way to "fork" a conversation and explore two directions independently

Proposed Solution

A simple command to duplicate the current conversation:

/clone

This would:

1. Create a copy of the current conversation with new UUIDs
2. The clone appears in claude -r (marked with [CLONED] or similar)
3. Both conversations continue independently

Use Cases

• Experimentation: Try implementing with approach A in one conversation and approach B in another
• Comparison: Try different prompts/instructions from the same starting point