Colour markdown's tables and the addresses written in it

A table is recognised by its delimiter row, the only line of one that cannot
be anything else, and its header is the line above -- the single place the
scanner looks ahead. Colouring every `|` instead would have marked the pipes
of a shell command written in a paragraph.

Addresses come in two shapes: `<...>` needs a scheme's colon or an at sign
inside it and no whitespace, which leaves `<div>` alone; a bare `scheme://`
needs no closer, so where it ends is the decision -- the sentence's trailing
punctuation is given back, and so is a closing bracket unless one opened
inside the URL.

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

TRANSCRIPT_RENDERING.md

@@ -253,7 +253,10 @@ and are the reason several tempting simplifications were rejected.
   not start or end inside a word (`snake_case_name`), and an indented code
   block is left plain, because four spaces after a blank line and four
   spaces after a bullet are the same line and only what came before tells
-  them apart.
+  them apart. A table is the one thing it looks ahead for: the delimiter row
+  (`|---|---|`) is the only line of one that cannot be anything else, and the
+  header belongs to the line before it -- which is what keeps the pipes of a
+  shell command written in a paragraph plain.
   It replaced dev.snipme:highlights 1.1.0 on 2026-09-03, which found
   comments before it knew the language and paired `/*` with `*/` by
   ordinal. That library used one set of delimiters for every language, so