[StephenSmith25]

Docs:

• index.md: accurate variable types, platforms (prebuilt: Windows/Linux x86_64), architecture, supported features and a real limitations list; remove links to the non-existent api.md and Discussions
• Quick-start and PID examples registered variables before creating the attributes / under different names, so inputs and parameters had no setter (PID would fail to build). Explain the create-then-register rule.
• usage.md: Fmi3StepResult fields table, logging, units, array-size note
• usageMX.md: what is required vs optional, value-reference numbering, update_discrete_states example now returns its result, result fields
• README: real pythonfmu3 build options, missing imports in the MX example
• install.md: build-from-source requirements and commands for all platforms
• changelog entries

Code:

• Fmi3UpdateDiscreteStatesResult used discreteStateNeedsUpdate and nominalsOfContinuousStatesChanged, but the wrapper reads the FMI names discreteStatesNeedUpdate / nominalContinuousStatesChanged, so both flags were silently ignored. Rename to the FMI names; keep the old ones as aliases.

Tests: test_docs now checks every documented model (all variables readable, inputs/parameters settable, model description builds), covers index.md, and skips instead of failing when run from an installed package.