Align error parser status codes with MT-SICS spec

[BioCam]

Summary

• _parse_basic_errors checked for status 'P' (not in MT-SICS spec) instead of 'L' (logical error, e.g. parameter not allowed)
• 'L' responses from the scale were silently ignored, meaning bad-parameter commands appeared to succeed
• Corrected docstring to match MT-SICS spec (p.10, sec 2.1.3.1): documents A, B, I, L, +, -
• Added TODO for B (multi-response) status handling

Verification

Hardware-tested on a WXS205SDU:

M21 99 99 -> b'M21 L\r\n'   (scale sends L, not P)
SI        -> b'S S    0.00006 g\r\n'  (normal read OK)
XYZNOTREAL -> b'ES\r\n'     (syntax error OK)
ZC 5000   -> b'ES\r\n'      (confirms ZC takes no params)

Test plan

• Simulated ['S', 'L'] response now correctly raises MettlerToledoError
• Simulated ['S', 'P'] no longer falsely caught
• Hardware-verified: real WXS205SDU returns L for invalid parameters
• All other status codes (I, +, -, ES, ET, EL) unchanged and working

🤖 Generated with Claude Code