Drop bytes input in 2.0; require str #245

Summary

2.0 should stop accepting bytes anywhere and require str, making decoding the caller's job. The bytes tolerance is a Python 2 legacy, and — verified below — it is already inconsistent to the point of being half-broken: bytes input currently gets a different behavior depending on which door it walks through.

Current state (verified)

So the "feature" is: two paths that decode, one that crashes confusingly despite an isinstance check that promises support, and one that's already banned. Nobody can be relying on the full surface, because part of it doesn't function.

Additional defect: environment-dependent decoding

SetManager.add_with_encoding resolves the encoding as encoding or sys.stdin.encoding or DEFAULT_ENCODING. The encoding of the process's stdin has no relationship to an arbitrary bytes argument, so the same call can decode differently depending on how the process was launched (terminal vs. pipe vs. embedded with sys.stdin = None). Library behavior should not vary with the runtime environment.

What's removed in 2.0

• full_name: str | bytes and original: str | bytes become str
• The encoding constructor kwarg and self.encoding attribute
• The bytes branch in _set_list and the bytes tolerance in parse_pieces (accepting what later crashes)
• add_with_encoding() — add() becomes str-only, raising the same decode-hint TypeError the constructor already raises; the stdin sniffing goes with it

Migration

One line at the boundary: HumanName(raw.decode('utf-8')) — the caller knows the real encoding; the library never did. Everything else is the same call with str.

Bridge

• DeprecationWarning when bytes reaches full_name or SetManager.add(), naming the decode-first replacement — shipped in 1.3.0 (Add 2.0 deprecation warnings for bytes input and SetManager legacy surface #253)

• 1.4: DeprecationWarning on every add_with_encoding() call regardless of argument type, naming add() as the replacement — the str path is silent today, so the method's removal is otherwise unwarned (bytes callers additionally get the existing decode-first warning; two distinct migrations). Tracked in Add 2.0 deprecation warnings for second-wave removals (1.4 sweep) #263.