docs: draft ten logo concepts

Eight fresh directions plus two refinements of the shipped mark, each
authored as a real currentColor SVG in the app's house style rather than
as a description, so any of them can be dropped straight in and the
favicon tile is a mechanical derivation.

Every mark was rendered at 120/32/24/16px and looked at, which changed
the set three times: the braid came out as a plain multiplication sign
and was rebuilt with actual over/under crossings, the anchor was
rebalanced to three-fold symmetry, and the first return-arc read even
more like a copyright glyph than the current one.

The finding that matters is not one of the eight. The mark shipping
today fails at 16px — its outer strokes drop out to rasterisation and
the 2.5px gap to the node fills in, so the favicon renders as a smear.
Concept 09 fixes that in five lines and is worth taking regardless of
whether anything here replaces the mark.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

docs/logo-concepts/07-knot.svg

@@ -0,0 +1,6 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" width="64" height="64" role="img" aria-label="Knot">
+  <title>Knot</title>
+  <!-- One continuous thread with no start and no end; it persists past any session. -->
+  <path d="M32 32C38 20 50 20 50 32 50 44 38 44 32 32 26 20 14 20 14 32 14 44 26 44 32 32Z"
+        fill="none" stroke="currentColor" stroke-width="6.5" stroke-linejoin="round"/>
+</svg>