[xibolun]

Summary

• serialize typed POST and PATCH models by field presence so omitted fields stay absent and explicitly supplied null values become JSON null
• preserve false, zero, empty strings, empty collections, nested explicit nulls, and raw dictionary payloads
• retain legacy manager behavior by omitting optional arguments that callers did not supply
• centralize manager-owned optional argument filtering and document the Serial Interface revalidation step
• add offline regression coverage for transport serialization and affected public manager APIs

User-facing Account behavior

Account models passed directly to add_account or update_account follow the same presence-aware rule as other typed models. Explicit construction such as Account(enabled=None) now sends Enabled as JSON null. In contrast, fields absent from Account.model_validate response data remain unset and are excluded from mutation payloads.

Validation

• 872 passed, 11 skipped, 109 subtests passed (tests/test_real_bmc.py excluded as an integration test)
• Ruff checks passed for changed source and tests
• source compilation passed
• source distribution and wheel builds passed

Closes #119