Verifies libplctag's GetString/SetString round-trips ST file strings (1-word
length prefix + 82 ASCII bytes) end-to-end through the driver, and adds a
client-side length guard so over-82-char writes return BadOutOfRange instead
of being silently truncated by libplctag.
- LibplctagLegacyTagRuntime.EncodeValue: throws ArgumentOutOfRangeException
for >82-char String writes (StFileMaxStringLength constant).
- AbLegacyDriver.WriteAsync: catches ArgumentOutOfRangeException and maps to
BadOutOfRange.
- AbLegacyStringEncodingTests: 16 unit tests covering empty / 41-char /
82-char / embedded-NUL / non-ASCII reads + writes; over-length writes
return BadOutOfRange and never call WriteAsync; both Slc500 and Plc5
family paths exercised.
Closes#249
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
