Halfwidth corner brackets (山田 ｢ﾀﾛｰ｣ ﾀﾛｳ) aren't read as a nickname #597

The full-width Japanese corner brackets 「」 are a default nickname delimiter (#273), but their halfwidth forms ｢｣ (U+FF62/U+FF63) are not. The bracketed word stays in the name as a middle name, brackets and all:

>>> from nameparser import parse
>>> parse("山田 「タロー」 太郎").nickname
'タロー'
>>> n = parse("山田 ｢ﾀﾛｰ｣ ﾀﾛｳ")
>>> n.nickname, n.middle
('', '｢ﾀﾛｰ｣')

The bracket also costs the name its order. The unclassified ｢ keeps the text from being wholly East Asian script, so 山田 ｢ﾀﾛｰ｣ ﾀﾛｳ reads given 山田, family ﾀﾛｳ. With the pair added, the clause is extracted and the rest reads family-first, as 山田 ﾀﾛｳ does since #594:

>>> from nameparser import Parser, Policy, DEFAULT_NICKNAME_DELIMITERS
>>> p = Parser(policy=Policy(nickname_delimiters=DEFAULT_NICKNAME_DELIMITERS | {("｢", "｣")}))
>>> n = p.parse("山田 ｢ﾀﾛｰ｣ ﾀﾛｳ")
>>> n.family, n.given, n.nickname
('山田', 'ﾀﾛｳ', 'ﾀﾛｰ')

Why it matters. Halfwidth brackets come from the same source as the halfwidth katakana #594 just classified: legacy JIS X 0201 data, where ｢｣ were the only corner brackets available. The PR #595 review found the gap.

Proposal. Add ("｢", "｣") to DEFAULT_NICKNAME_DELIMITERS, beside 「」.

• Rationale: the halfwidth pair is the same punctuation as 「」 in a narrower encoding, and appears in no non-CJK text.
• Boundaries: John ｢Jack｣ Smith would read nickname Jack like John 「Jack」 Smith already does. Measured today, it reads middle ｢Jack｣.
• Nothing else needs a halfwidth twin. Unicode has no halfwidth form of 『』 or of the full-width parentheses.
• Accepted consequences: this changes a default, so it's a release-log-classified behavior change. Every ｢…｣ input moves, so the differential needs a case row and a ledger rule.
• Open question: whether the v1 facade should gain a matching sentinel key in nickname_delimiters. Support smart quotes (“Jack”), guillemets («Petit»), and CJK brackets as nickname delimiters #273's eight typographic pairs each got one (_SENTINEL_PAIRS). Today HumanName("山田 ｢ﾀﾛｰ｣ ﾀﾛｳ") reads middle ｢ﾀﾛｰ｣.