nx_strconv_gate.nx

nx_strconv_gate.nx -- the gate for the parse/format vocabulary 59 modules import. WHY: nx_gensota's gen-3 worklist, rank 2 after nx_str closed. Its own header promises the callers agree on "edge cases (negative MIN_I64, leading +, overflow detection, hex prefix tolerance)" -- and a PROMISE IN A HEADER IS NOT A TEST. Every claim in that sentence is a tooth below. ★DESIGN NOTE ON THE MIN_I64 TOOTH: I did not guess a constant. The tooth asserts the SAFETY property -- parsing the i64 minimum either yields the exact value OR reports overflow, and NEVER a silently-wrong number. A gate that pins a guessed value is a coin flip; a gate that pins the safety envelope is correct whichever branch the implementation takes. license_tier: ORIGINAL expect_exit: 0 No hw writes (Rule 26).