fix(web): repair + dedup the web demo (regression + pre-existing breakage)

GitHub Pages serves from root (path /). The live demo's root index.html
imported ./printable_binary.js, which did not exist at root -> demo broken.
Separately, docs/printable_binary.js was a stale FORK of js/printable_binary.js
whose parser predated the ## comment support, so it mis-mapped the first 19
bytes to comment text once character_map.txt gained its header.

Fix by making js/printable_binary.js the single source for the web too:
- printable_binary.js            -> symlink js/printable_binary.js  (fixes live demo)
- docs/printable_binary.js       -> symlink ../js/printable_binary.js (removes the 6th
                                    parser + 7th map-table copy; fixes the comment regression)
- docs/index.html                -> symlink ../index.html (was byte-identical dup)
- add .nojekyll so Pages serves the symlinks/underscored paths

Verified via the real browser module path (node): byte0='·' (comments filtered),
encode([0x00,0x20])='·␣', full roundtrip OK.

Author: pmarreck