Make the brand icon the bare figure everywhere, matching the site logo

The repo's app-icon files still had the figure inside a dark rounded tile,
while the site nav uses the bare figure — so the logo looked inconsistent
between the webpage and the repo. Unify on the bare figure (flat lime, the
exact nav mark): no tile anywhere.

- favicon.svg is now the bare figure, color-adaptive (lime on dark UI, ink on
  light) so it stays legible in the tab without a background.
- Re-rendered favicon-16/32/48/192/512 and docs/brand/posecode-icon-512.png as
  the bare lime figure on transparent; the social banner uses the bare figure
  on the dark gradient. apple-touch stays a lime figure on flat dark (iOS
  requires an opaque icon).
- Simplified docs/brand to one logo concept: removed the tiled posecode-icon.svg,
  posecode-icon-360.png, and the duplicate posecode-mark-512.png; updated the
  README.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01B7RkyiTt9soiYdw5vt6BEP

Author: claude

docs/brand/README.md

@@ -1,39 +1,38 @@
 # Posecode brand kit
 
-The Posecode mark is a **kinematic figure in an open, energetic pose**: bones are
-strokes, joints are markers, the same rig the app animates. It hints at the
-project (human movement + a technical rig) while staying friendly and legible
-down to 16px.
+The Posecode logo is a **kinematic figure in an open, energetic pose**: bones as
+strokes, joints connected, the same rig the app animates. It hints at the
+project (human movement) while staying friendly and legible down to 16px. It is
+the exact mark used in the site's nav, favicon, and app icon: one logo,
+everywhere, no separate "tiled" variant.
 
 ## Palette
 
 | Token | Hex | Use |
 | --- | --- | --- |
 | Lime | `#c6f24a` | The figure / accent |
-| Lime (light) | `#d6ff5e` | Top of the figure gradient |
-| Lime (deep) | `#a9e02f` | Bottom of the figure gradient |
-| Ink | `#0a0d12` | Dark background / tile |
+| Ink | `#0a0d12` | Dark background |
 
 Type: **Hanken Grotesk** (wordmark), **JetBrains Mono** (code).
 
 ## Files
 
 | File | What it is |
 | --- | --- |
-| `posecode-mark.svg` | Figure only, `currentColor` (inherits text color). For inline logos. |
-| `posecode-mark-512.png` | Figure only, lime, transparent background. |
-| `posecode-icon.svg` | Rounded dark app-icon tile with glow + joint markers. |
-| `posecode-icon-512.png` | The app icon, rendered, transparent corners. Good for avatars. |
-| `posecode-icon-360.png` | Full-bleed square (no rounded corners) for iOS / masked contexts. |
-| `posecode-social.png` | 1280×640 GitHub social preview (mark + wordmark + tagline). |
+| `posecode-mark.svg` | The logo, `currentColor` so it inherits the surrounding text color. Source of truth for inline use. |
+| `posecode-icon-512.png` | The logo as a flat-lime PNG on a transparent background. Use for READMEs, avatars, anywhere. |
+| `posecode-social.png` | 1280×640 GitHub social preview (logo + wordmark + tagline). |
 
-The live favicon (`playground/public/favicon.svg`) and iOS icon
-(`playground/public/apple-touch-icon.png`) are wired into the site.
+The live favicon (`playground/public/favicon.svg`, plus `favicon-16/32/48/192/512.png`)
+and the iOS icon (`playground/public/apple-touch-icon.png`) use this same figure.
+The SVG favicon adapts to the tab color (lime on dark UI, ink on light) so it
+stays legible without a background tile.
 
 ## Using them on GitHub
 
 - **Repo social preview:** Settings → General → Social preview → upload
   `posecode-social.png`.
-- **Org / project avatar:** upload `posecode-icon-512.png` (square, rounded) or
-  `posecode-icon-360.png` (full-bleed).
-- **README badge / inline:** reference `posecode-mark-512.png`.
+- **Org / project avatar:** upload `posecode-icon-512.png`. (It's transparent, so
+  on a light avatar background the lime figure will read light; if you want more
+  contrast there, place it on an `#0a0d12` square first.)
+- **README / inline:** reference `posecode-icon-512.png` or `posecode-mark.svg`.