Board: add page <title> (Republic OS — The Board)

The page had no <title>, so browser tabs / the Artifact fell back to the
filename. build_viz.py's injection only rewrites the const lines, so the
title is preserved across regenerations.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

viz/board.html

@@ -1,3 +1,4 @@
+<title>Republic OS — The Board</title>
 <style>
   :root{
     --ground:#0a0f16; --panel:#0f1620; --panel2:#0c121b;