url: improve recall for localhost, IP literals, uppercase TLDs #6

URL parsing misses several common and structurally unambiguous forms.

Gaps

• http://localhost:3000/ — full-URL grammar requires an IANA TLD (src/URL.ts:95-103)
• https://127.0.0.1:8443/a — no IPv4 literal support
• https://[2001:db8::1]/x — no bracketed IPv6 support
• https://my-site.EXAMPLE.COM/ — host labels reject hyphens (src/URL.ts:75-93), TLD matching is lowercase-only (tests/URL.test.ts:170-174 currently locks in this false negative)
• Ports use generic number() (src/URL.ts:67-69): accepts :1.5-style input and can swallow a trailing sentence period; no 1-65535 range check
• Lone trailing / is dropped (src/URL.ts:70-74)
• Suffix [^\s]+ absorbs closing quotes/brackets/periods into the URL span

Proposal

• Split authority handling: protocol-qualified URLs accept valid DNS names (with internal hyphens), localhost, IPv4, bracketed IPv6, and internal/registered names without requiring an IANA TLD; keep the IANA-TLD requirement for bare domains only
• Case-insensitive TLD/host matching; support Punycode and Unicode labels
• Parse port as integer, validate 1-65535
• Accept a lone /
• Scan suffix permissively, then trim clearly unmatched trailing sentence punctuation (keep balanced URL punctuation)

Tests to add

• https://my-site.EXAMPLE.COM/, http://localhost:3000/, https://127.0.0.1:8443/a, https://[2001:db8::1]/x, https://münchen.de/, https://xn--mnchen-3ya.de/
• See https://example.com/a). → span excludes ).
• :1.5 and :65536 rejected as ports
• Flip the lowercase-only TLD expectation at tests/URL.test.ts:170-174

Perf note
Bound labels (63), authority, and total domain length (253) while touching this grammar — see also the superlinear-scan issue for dotted non-matches.