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>

.agent/skills/bmad-ux/references/design-md-spec.md

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+# DESIGN.md Spec — Working Reference
+
+Source of truth: [google-labs-code/design.md](https://github.com/google-labs-code/design.md) (Apache 2.0, Google Labs, April 2026). This file is a working summary; the URL wins on conflict.
+
+## Structure
+
+YAML frontmatter (machine-readable tokens) + markdown body (human-readable rationale, prose sections).
+
+## Frontmatter tokens
+
+| Key | Type | Notes |
+|---|---|---|
+| `name` | string | Required. Brand or system name. |
+| `description` | string | One-line statement of what this system is. |
+| `colors` | flat object | Kebab-case keys. Values are hex strings (`'#FBF9F4'`). |
+| `typography` | nested object | Each value: an object with any subset of `fontFamily`, `fontSize`, `fontWeight`, `lineHeight`, `letterSpacing`. |
+| `rounded` | object | Scale names (`sm`, `md`, `lg`, `xl`, `full`, `DEFAULT`) → CSS dimensions. `full` is conventionally `9999px`. |
+| `spacing` | object | Scale levels (`'1'`, `'2'`, ...) or named tokens (`gutter`, `margin-mobile`, `editorial-gap`) → dimensions. |
+| `components` | object | Component-name → object of component tokens mapped to values or `{path.to.token}` references. |
+
+## Body sections (omittable, order-locked when present)
+
+1. **Brand & Style** — Aesthetic posture in prose. The editorial voice — what *kind* of thing this is.
+2. **Colors** — Per-color story. Why each exists, where it's used, what it's *not* used for.
+3. **Typography** — Type roles, ramp, and rules. Platform conventions noted semantically when inherited.
+4. **Layout & Spacing** — Spacing scale narrative, grid behavior, margins, gutters, breakpoint rules.
+5. **Elevation & Depth** — Shadow language and tonal layering rules.
+6. **Shapes** — Corner radii rules and the aesthetic logic behind them.
+7. **Components** — Per-component visual specs: anatomy, color usage, sizing, state appearance.
+8. **Do's and Don'ts** — Hard visual rules — what to do, what to avoid.
+
+Sections may be omitted when not relevant; order is locked when present.
+
+## Cross-reference syntax
+
+`{path.to.token}` used in prose and inside component objects to reference frontmatter tokens. Examples:
+
+- `{colors.primary}`
+- `{typography.body.fontSize}`
+- `{rounded.md}`
+- `{spacing.4}`
+
+The path follows the YAML structure.
+
+## Common patterns
+
+- **Light/dark mode.** Either separate kebab-case tokens (`surface-base` / `surface-base-dark`) or separate DESIGN.md files per mode. The spec allows either; pick the form that reads cleanest for the product.
+- **Platform conventions.** When inheriting from native platforms (iOS UIKit, Android Compose, Apple Human Interface Guidelines), use a `note` field instead of literal values: `{ note: 'iOS Title 1 · Android Headline Small' }`. The spec is the spec; the platform owns the rendered values.
+- **UI-system inheritance.** When inheriting from shadcn / MUI / Tailwind / internal design system, reference the system's tokens by name rather than restating values. DESIGN.md specifies only the deltas (brand color overrides, typography swaps, component customizations).
+- **Component tokens.** The `components` frontmatter entry maps each named component (e.g., `button-primary`) to its specific token values. Use `{path.to.token}` references freely; the resolver flattens at consumption time.