parser: +fix Malformed .mata input only validated by asserts, crashes Release builds

[Adda0]

The .mata parser validated input structure only with assert(), which vanishes in
Release builds (-DNDEBUG). Malformed input caused out-of-bounds reads (segfaults)
or was silently misparsed, instead of raising an error naming the offending
construct.

This commit replaces input-validating asserts with real checks that throw
std::runtime_error, while keeping asserts only for genuine internal invariants
(not input shape).

Fixed validations:

• get_naming_type(): throw on unknown suffix (auto, enum, marked, chars, utf)
• get_alphabet_type(): throw on unknown suffix (bits, explicit, intervals)
• mf_to_aut(): throw on unknown automaton type (NFA, AFA, NFT)
• parse_transition(): throw when transition tokens < 2, or < 3 for explicit NFA/NFT
• ParsedSection::operator[]: throw when key is missing instead of returning garbage
• builder::construct(IntermediateAut, Alphabet*): throw on null alphabet

Bare @NFA and %Alphabet without suffix continue to be accepted for Release
compatibility; Debug now accepts them too via explicit empty-suffix checks.

Python bindings: added except + to parse_from_mf, construct, and mintermize
in parser.pxd so C++ exceptions surface as Python exceptions rather than crashes.

BEFORE (Release build):

• malformed transition "q0": SIGSEGV
• malformed transition "q0 1": SIGSEGV (out-of-bounds rhs[1])
• malformed transition "q0 1 q1 q2": silently dropped q2, accepted
• bad alphabet type "bitz": accepted as explicit
• bad naming "States-numbers": misinterpreted as "States-auto"
• sec["Final"] on missing key: returned garbage size

AFTER:

• malformed transition cases: throw std::runtime_error
• bad type suffixes: throw std::runtime_error
• ParsedSection["missing"]: throw std::runtime_error

Fixes #761.

Fixes #761