Add sales growth paths documentation

Documents three growth trajectories for sales personas:
- Kendall: Entry-level rep learning path
- Gage: Senior AE account expansion strategy
- Jess: Sales manager team transformation

Shows how automated demos enable scalable, repeatable selling.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Tony Hansmann