#15 hu13 logo (svg + ascii)

Context: hu13 has no identity. Navbar integration (#16) and favicon (#17) both need the logo first — this issue unblocks them. Tasks:

1. Design a hu13 ("hub") logo: sharp, geometric, no rounded corners, Tokyo Night palette (bg #1a1b26, fg #c0caf5, accent blue #7aa2f7 / cyan #7dcfff). Must read at 16px (favicon) and 32px+ (navbar). Deliver static/logo.svg (hand-written, tiny, no build step) + a wordmark variant. No gradients that muddy at small sizes.
2. ASCII variant for README/wiki (banner reading hu13, ≤12 lines, ≤60 cols, plain hyphens/slashes/pipes aesthetic matching sharp-corner brand).
3. Tests: logo.svg exists + valid XML + <2KB; README-ascii block renders inside <pre> unescaped-except-esc(). Success rubric:

• logo.svg valid, tiny, legible description in summary (shapes used).
• ASCII art constant available for wiki README (#19) and agents page. Swarm: Owl with taste. Branch m6/logo.