Snapshot WIP: solver HP epic progress, BPHX/HX physics, BMAD skill refresh.

Capture uncommitted solver robustness work (regularization, domain errors, linear solver lifecycle, tube DP/MSH), web workbench updates, and synced BMAD skills across IDE agent folders before starting BPHX pressure-drop.

Co-authored-by: Cursor <cursoragent@cursor.com>

.claude/skills/bmad-ux/assets/design-example-mobile.md

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+---
+name: Quill
+description: Daily writing companion. Calm, intentional, dark-mode-by-default. No streaks, no gamification.
+colors:
+  surface-base: '#FAF9F7'
+  surface-raised: '#FFFFFF'
+  ink-primary: '#1A1B1F'
+  ink-secondary: '#6B655A'
+  ink-disabled: '#B5AFA5'
+  accent: '#A87434'
+  border-hairline: '#E8E4DD'
+  surface-base-dark: '#1A1B1F'
+  surface-raised-dark: '#23252B'
+  ink-primary-dark: '#F0EDE8'
+  ink-secondary-dark: '#A39E94'
+  ink-disabled-dark: '#5E5A53'
+  accent-dark: '#D4A574'
+  border-hairline-dark: '#2E3036'
+typography:
+  title:
+    note: 'Platform native — iOS Title 1 · Android Headline Small'
+  body:
+    note: 'Platform native — iOS Body · Android Body Large'
+  meta:
+    note: 'Platform native — iOS Footnote · Android Body Small'
+rounded:
+  sm: 6px
+  md: 12px
+spacing:
+  '1': 4px
+  '2': 8px
+  '3': 12px
+  '4': 16px
+  '5': 24px
+  '6': 32px
+---
+
+## Brand & Style
+
+Quill is designed against the grain of contemporary habit apps. Where most products weaponize the user's calendar with streak counters and re-engagement nudges, Quill insists on something quieter — a daily prompt, a place to write, and the unspoken assurance that today's entry is enough. Showing up is the point, not the streak.
+
+The visual language follows. Calm surfaces in warm off-white (light) or deep ink (dark, the default). Generous breathing room. No chromatic color competing for attention except a single warm tobacco that signals save-and-send. Text-first. Hand-on-paper, not buzz-on-screen.
+
+## Colors
+
+The palette is restrained on purpose — a writing surface should not compete with the writing.
+
+- **Warm White (`#FAF9F7`)** is the primary canvas in light mode. Slightly warm to reduce eye strain and keep the surface from feeling clinical.
+- **Deep Ink (`#1A1B1F`)** is the dark-mode canvas and the primary body text color in light mode. Quill defaults to dark because most writing happens at night.
+- **Tobacco (`#A87434` light / `#D4A574` dark)** is the only chromatic color. Used exclusively for the save indicator and primary action — never for decoration, never for state badges.
+- **Hairline (`#E8E4DD` light / `#2E3036` dark)** separates list items at the lowest possible contrast. Anything heavier feels like UI rather than paper.
+
+Avoid: red error fills (Quill is a journal, not a form), gradients (the surface is paper), and saturated accent variants — one accent, used sparingly.
+
+## Typography
+
+Platform conventions are the spec. iOS uses Title 1 / Body / Footnote; Android uses Headline Small / Body Large / Body Small. Dynamic type honored at every level — the largest accessibility setting must still render legibly without truncation.
+
+Headlines are rare. The Today prompt is set in `title`; everything else is `body` or `meta`. No display sizes, no all-caps labels.
+
+## Layout & Spacing
+
+Scale: 4 / 8 / 12 / 16 / 24 / 32 px. The largest gaps land between major surfaces; the smallest sit between tightly related elements. Vertical rhythm follows a hard rule: composer breathes, list items don't.
+
+Mobile margins follow platform conventions (iOS 16pt, Android 16dp). Single-column always; modal stacks one level deep, never two.
+
+## Elevation & Depth
+
+Quill avoids elevation as a visual device. Cards and composer surfaces sit on `surface-raised`, distinguished from `surface-base` only by tone. Shadows are reserved for the rare moment of literal physical metaphor — never for hierarchy. Hierarchy comes from layout and typography, not shadow.
+
+## Shapes
+
+`rounded/sm` (6px) for inputs, list rows, and small surfaces. `rounded/md` (12px) for cards and the composer. Nothing fully rounded; no pills, no perfect circles for surfaces. The aesthetic is paper-with-soft-corners, not iOS-button-pill.
+
+Imagery follows container corners exactly.
+
+## Components
+
+- **Prompt card** — `surface-raised`. One per day. Today's prompt in `title`. Tap to open composer. No icon, no decoration; the prompt itself is the affordance.
+- **Composer** — Full-screen text view. Clean text field, generous vertical padding, single-line save indicator in the header.
+- **Save indicator** — Text only. Uses `ink-secondary`, never a checkmark icon, never a colored badge.
+- **Entry row** (Library) — Date in `meta`, first line of body in `body` (truncated to one line). Hairline divider only, no fill.
+- **Settings row** — Label left, value or chevron right. Tobacco accent only on destructive confirmations.
+
+## Do's and Don'ts
+
+| Do | Don't |
+|---|---|
+| Single accent color, used sparingly on save & primary action | Color-code by sentiment, mood, or category |
+| Text-only state indicators (`Saved.`) | Iconography for state (✓, ⚠, ●) |
+| Hairline dividers at lowest legible contrast | Card shadows, gradient fills, accent fills behind text |
+| Generous vertical rhythm in composer | Compress to fit more on screen |
+| Honor platform conventions for navigation | Override platform nav with custom drawer or hamburger |