Harden RowBinary boundary validation - #410

Summary

• reject Decimal, float, date/time, and network values before fixed-width RowBinary encoding can wrap, truncate, or become non-finite
• escape and parse hostile Enum labels losslessly, and reject invalid or ambiguous Enum/Decimal type definitions
• add focused boundary and property suites plus a live ClickHouse Enum escaping regression

Corruption and robustness fixes

The adversarial tests expose and fix these cases:

• Decimal32/64/128/256 coefficients could wrap at their signed storage width; specifically, Decimal32 values 2147483648 and 4294967296 became -2147483648 and 0
• scaling and rounding could introduce unchecked Decimal overflow
• declared Decimal precision and scale were not enforced for RowBinary
• non-finite Decimals raised incidental arithmetic errors
• Float32 overflow encoded infinity, which decoded as nil
• Date and DateTime values wrapped their UInt16/UInt32 storage
• DateTime64 ticks could overflow Int64
• IPv6 segments silently truncated; invalid IPv4 octets returned invalid iodata
• Enum labels containing quotes, backslashes, delimiters, controls, or NUL were not escaped or decoded correctly
• invalid or duplicate Enum mappings and invalid Decimal definitions were accepted

Adversarial coverage

• generated signed bit patterns for every Decimal storage width
• exact min/max and one-past-boundary cases
• scaling, rounding, precision, exponent, and non-finite Decimal cases
• Float32/Float64 overflow cases
• Date, DateTime, and DateTime64 storage boundaries
• generated IPv4 octets and every IPv6 segment bit pattern
• generated Enum type round-trips with quotes, backslashes, punctuation, whitespace, controls, Unicode, and NUL
• live ClickHouse insert/select using escaped Enum RowBinary type headers in both connection modes

This branch is rebased onto current master. The reverted API/test-ownership refactor is intentionally not included; the live Enum regression now lives in the restored connection_test.exs suite.

Verification

• focused boundary suite: 243 passed (159 doctests, 4 properties, 80 tests)
• live Enum escaping regression: 2 passed (both connection modes)
• isolated full suite: 638/640 passed; the two untouched socket-timeout cases that flaked passed 4/4 on immediate isolated rerun
• slow tests: 5 passed
• dependency lock and unused dependency checks pass
• compile with warnings as errors passes
• format check passes
• Dialyzer: 0 errors
• git diff --check passes