Left becomes a full-height .planning-sidebar (Missions-matched surface/border/width) with a scrolling list and a bottom-pinned footer; New Session moves to that footer using btn btn-primary (same CTA tokens as the Missions create button — size/color match). Right .planning-detail fills remaining width + full height, so it reads as a true two-pane view. Non-embedded modal presentation unchanged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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