Session volume profile / TPO as a first-class pane #39

Part of the percept.one parity roadmap.

Problem

The only volume-at-price visualization today is the manually drawn Fixed Range Volume Profile drawing (drawings/forecasting.ts:267-318, 24 rows, POC + value area). Percept ships session profiles and TPO natively.

Work

• Auto-updating session volume profile pane (composite + per-session split)
• TPO / market profile renderer
• POC, value area high/low lines projected on the main pane
• Reuse the volume-profile math from the existing drawing

Completion audit

Verified on main in merged PR #41: attachSessionProfile provides auto-updating composite or per-session volume/TPO panes and main-pane POC/VAH/VAL projections. Shared math in core/profile.ts is reused by the fixed-range drawing. Covered by session-profile and profile-math tests.

Validation: the existing main suite passed 1,849 tests with 100% line, branch and function coverage; PR #41 main coverage and documentation workflows both passed.