A bare URL is read with no left-boundary guard where the reference requires a line start, a blank or a bracket before the scheme

What happens

BARE_ADDRESS in src/parse/inline/rules.ts has no left-boundary guard. Ruby's InlineLinkRx (rx.rb l.526) requires (^|link:|blank|[>()\[\];"']) in front of the scheme; our rule matches anywhere, so xftp://e.com/a tokenizes as text plus a URL where the reference reads one plain text run. Byte-neutral today (the link node replays the author's bytes), so a tree divergence only; the #214 change widened the scheme list from two to five (https?, file, ftp, irc), which enlarged the surface. Sibling of the trailing-punctuation difference already commented in the same rule. Found by the #214 change (2026-09-06).

Fix shape

Add the left-boundary lookbehind to the rule and cite the line; measure the boundary class through both programs first (the bare-URL left boundary is a FREE slot in the whitespace battery, rx.rb l.526).

Start in src/parse/inline/rules.ts at BARE_ADDRESS, then compare the reference boundary in rx.rb line 526. Measure the left-boundary class through both programs using the whitespace battery, and verify that cases such as xftp://e.com/a remain one plain-text run while valid boundaries still tokenize as URLs.