Draft TradingView overlay export format

[zrack]

Research and propose a simple export format for overlaying gex-terminal levels on TradingView.

Acceptance criteria:

• Include gamma wall, zero-gamma, call wall, put wall, and major exposure bands.
• Prefer a simple portable format such as JSON or CSV first.
• Document how a user could manually translate exported levels into chart annotations.
• Call out what would require a Pine Script or external integration later.