TupleManager unknown-key access silently returns None / EMPTY_REGEX; raise AttributeError in 2.0 #256

The last member of the silent-config-typo family the 1.3.0 cycle exterminated (#238, #241, #242, #244). TupleManager.__getattr__ returns self.get(attr) — None for any typo'd key — and RegexTupleManager returns EMPTY_REGEX, which matches the empty string at every position:

CONSTANTS.regexes.parenthesys                  # EMPTY_REGEX — no error, matches everywhere
CONSTANTS.capitalization_exceptions.phd_typo   # None — no error

A misspelled regex override silently degrades parsing with no traceback pointing at the typo. (The dunder-probe guards added earlier protect copy/pickle protocols but not user typos.)

2.0: unknown attribute access raises AttributeError naming the known keys, mirroring parse_nicknames()'s existing fail-loud style. dict.get() remains available for intentional soft access. The nickname_delimiters/maiden_delimiters string sentinels are unaffected — they membership-check before resolving.

Bridge (1.4) — tracked in #263

• DeprecationWarning on unknown-key attribute access, naming the miss and the known keys