id: UX-001
title: Full-Width Two-Pane Page Layout
status: done
priority: P1
effort: M
depends_on:
  - PORT-004
  - BT-001A
  - BT-003A
tags:
  - ui
  - layout
  - nicegui
summary: Use the full available browser width and standardize primary pages on a 1/3 control-summary pane and 2/3 charts-results pane.
completed_notes:
  - Added a shared `split_page_panes(...)` helper in `app/pages/common.py` and removed the old centered max-width dashboard container.
  - Applied the full-width two-pane layout to overview, hedge, backtests, event comparison, options, and settings pages.
  - Fixed desktop pane overflow by switching the shared helper to a shrinkable 1:2 flex split instead of fixed width fractions plus gap.
  - Historical scenario pages now mark prior right-pane output as stale when inputs change instead of silently showing old results beside new left-pane summaries.
  - Event comparison now preserves manual template/unit edits across preview refreshes except when the preset itself changes and intentionally resets defaults.
  - Added browser-visible Playwright coverage for desktop pane ratios, no-horizontal-overflow checks, stacked narrow-width behavior, and stale-result states.