Add exact-height accordion to day sections

.impeccable.md

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+## Design Context
+
+### Users
+
+BusyWeek is for people doing quick, date-aware personal planning, primarily on a phone and secondarily in a desktop browser. They need to capture a thought quickly, see the whole wording later, mark it complete, and move it to another date without learning a project-management system.
+
+### Brand Personality
+
+Playful, energetic, and reassuring. The bilingual “BusyWeek! / 好忙啊” identity should make a busy schedule feel approachable rather than corporate or anxious.
+
+### Aesthetic Direction
+
+Preserve the product's recognizable Material-era blue gradient, white date cards, coral add action, rounded touch targets, and light motion. Native iOS is the primary interaction reference; Web is a faithful responsive companion rather than a separate redesign. New work should feel like a careful continuation of the existing app, not a generic modern productivity dashboard.
+
+### Design Principles
+
+1. Make capture immediate: opening, typing, choosing a date, and saving should stay within thumb reach.
+2. Preserve the user's words: Todo rows expand to show the complete text instead of truncating it to an arbitrary line count.
+3. Let motion explain change: inserts, removals, filtering, and date moves should visibly carry surrounding rows into their new positions.
+4. Prefer deliberate touch interactions: destructive and edit actions must not collide with checkbox taps or scrolling; long press is reserved for full Todo editing.
+5. Keep one interaction model across Native and Web while adapting measurement, keyboard avoidance, and responsive geometry to each platform.