brand: convert the wordmark to outlines

The four brand files were authored with live <text> set in IBM Plex Sans, and
the proof sheet closed on that being the one thing still to do before they were
used anywhere. It matters more than it sounds: the mark *is* the weight contrast
between Self at 200 and Post at 600, and a machine without Plex resolves neither
weight — browsers synthesise bold but never light, so the two words come out the
same and the wordmark stops being one. Almost no viewer has the font installed.

Laid out from the font's own metrics the way a browser would (advance widths
from hmtx, CSS letter-spacing after every character including the last, the
anchor centred on the result) and emitted as one path per text element, so the
files now render as drawn with no font installed at all. The note at the foot of
the proof sheet records that, and its file list is corrected to docs/assets/,
where these have lived since they were added.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/assets/selfpost-icon-16.svg

@@ -1,7 +1,8 @@
 <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" width="64" height="64" role="img" aria-label="SelfPost">
 <!-- SelfPost · https://codeberg.org/mix/selfpost · AGPL-3.0
-     Шрифт: IBM Plex Sans (OFL). Перед публикацией текст перевести в контуры. -->
-<path d="M7.80 5.00 L13.00 5.00 A2.8 2.8 0 0 0 18.60 5.00 L23.80 5.00 A2.8 2.8 0 0 0 29.40 5.00 L34.60 5.00 A2.8 2.8 0 0 0 40.20 5.00 L45.40 5.00 A2.8 2.8 0 0 0 51.00 5.00 L56.20 5.00 A2.8 2.8 0 0 0 59.00 7.80 L59.00 13.00 A2.8 2.8 0 0 0 59.00 18.60 L59.00 23.80 A2.8 2.8 0 0 0 59.00 29.40 L59.00 34.60 A2.8 2.8 0 0 0 59.00 40.20 L59.00 45.40 A2.8 2.8 0 0 0 59.00 51.00 L59.00 56.20 A2.8 2.8 0 0 0 56.20 59.00 L51.00 59.00 A2.8 2.8 0 0 0 45.40 59.00 L40.20 59.00 A2.8 2.8 0 0 0 34.60 59.00 L29.40 59.00 A2.8 2.8 0 0 0 23.80 59.00 L18.60 59.00 A2.8 2.8 0 0 0 13.00 59.00 L7.80 59.00 A2.8 2.8 0 0 0 5.00 56.20 L5.00 51.00 A2.8 2.8 0 0 0 5.00 45.40 L5.00 40.20 A2.8 2.8 0 0 0 5.00 34.60 L5.00 29.40 A2.8 2.8 0 0 0 5.00 23.80 L5.00 18.60 A2.8 2.8 0 0 0 5.00 13.00 L5.00 7.80 A2.8 2.8 0 0 0 7.80 5.00 Z" fill="#F3EDE1" stroke="#12161C" stroke-width="0.8" stroke-linejoin="round"/>
-<rect x="11" y="11" width="42" height="42" fill="#7A3B2E"/>
-<text x="32" y="43" text-anchor="middle" font-family="'IBM Plex Sans','Helvetica Neue',sans-serif" font-size="26" letter-spacing="-1" fill="#F6EDE2"><tspan font-weight="200">S</tspan><tspan font-weight="600">P</tspan></text>
-</svg>
+     Wordmark set in IBM Plex Sans (OFL) and converted to outlines: the
+     file needs no font installed to render as drawn. -->
+<path d="M7.80 5.00 L13.00 5.00 A2.8 2.8 0 0 0 18.60 5.00 L23.80 5.00 A2.8 2.8 0 0 0 29.40 5.00 L34.60 5.00 A2.8 2.8 0 0 0 40.20 5.00 L45.40 5.00 A2.8 2.8 0 0 0 51.00 5.00 L56.20 5.00 A2.8 2.8 0 0 0 59.00 7.80 L59.00 13.00 A2.8 2.8 0 0 0 59.00 18.60 L59.00 23.80 A2.8 2.8 0 0 0 59.00 29.40 L59.00 34.60 A2.8 2.8 0 0 0 59.00 40.20 L59.00 45.40 A2.8 2.8 0 0 0 59.00 51.00 L59.00 56.20 A2.8 2.8 0 0 0 56.20 59.00 L51.00 59.00 A2.8 2.8 0 0 0 45.40 59.00 L40.20 59.00 A2.8 2.8 0 0 0 34.60 59.00 L29.40 59.00 A2.8 2.8 0 0 0 23.80 59.00 L18.60 59.00 A2.8 2.8 0 0 0 13.00 59.00 L7.80 59.00 A2.8 2.8 0 0 0 5.00 56.20 L5.00 51.00 A2.8 2.8 0 0 0 5.00 45.40 L5.00 40.20 A2.8 2.8 0 0 0 5.00 34.60 L5.00 29.40 A2.8 2.8 0 0 0 5.00 23.80 L5.00 18.60 A2.8 2.8 0 0 0 5.00 13.00 L5.00 7.80 A2.8 2.8 0 0 0 7.80 5.00 Z" fill="#F3EDE1" stroke="#12161C" stroke-width="0.8" stroke-linejoin="round" />
+<rect x="11" y="11" width="42" height="42" fill="#7A3B2E" />
+<path d="M24.71 43.31Q22.47 43.31 21.01 42.47Q19.56 41.62 18.54 40.3L19.27 39.72Q20.23 40.97 21.49 41.71Q22.76 42.45 24.73 42.45Q26.99 42.45 28.23 41.39Q29.46 40.32 29.46 38.32Q29.46 36.94 28.94 36.15Q28.42 35.36 27.51 34.94Q26.6 34.52 25.49 34.29L23.74 33.95Q21.95 33.61 20.92 32.93Q19.9 32.24 19.44 31.29Q18.99 30.34 18.99 29.22Q18.99 27.63 19.69 26.59Q20.39 25.55 21.66 25.05Q22.94 24.54 24.63 24.54Q26.66 24.54 28.01 25.24Q29.36 25.94 30.14 27.11L29.41 27.66Q28.63 26.54 27.46 25.97Q26.29 25.4 24.58 25.4Q22.42 25.4 21.18 26.33Q19.95 27.27 19.95 29.19Q19.95 30.47 20.48 31.23Q21.01 32 21.92 32.42Q22.83 32.83 23.95 33.07L25.69 33.41Q27.54 33.74 28.57 34.46Q29.59 35.17 30 36.15Q30.4 37.12 30.4 38.24Q30.4 39.91 29.71 41.02Q29.02 42.14 27.73 42.73Q26.45 43.31 24.71 43.31Z M36.45 43H33.01V24.85H41.18Q42.87 24.85 44.06 25.55Q45.26 26.26 45.91 27.52Q46.56 28.78 46.56 30.47Q46.56 32.16 45.91 33.42Q45.26 34.68 44.06 35.38Q42.87 36.08 41.18 36.08H36.45ZM36.45 27.84V33.12H40.87Q41.54 33.12 42.01 32.87Q42.48 32.63 42.74 32.17Q43 31.72 43 31.07V29.87Q43 29.19 42.74 28.75Q42.48 28.31 42.01 28.08Q41.54 27.84 40.87 27.84Z" fill="#F6EDE2" />
+</svg>