Add typed value getters to States container

[iMicknl]

Resolves #2113. Follows on from #2108.

States.get_value() / first_value() return the untyped StateType union, so consumers needing a concrete type have to cast or do a get() + None-guard + value_as_* two-step (~52 cast(...) sites in the Home Assistant overkiz migration).

This adds thin pass-throughs on States that delegate to the existing State.value_as_* properties:

temperature = device.states.get_value_as_float(OverkizState.CORE_TEMPERATURE)  # float | None

orientation = device.states.first_value_as_int(
    [OverkizState.CORE_SLATS_ORIENTATION, OverkizState.CORE_SLATE_ORIENTATION]
)  # int | None

Six get_value_as_* (single key) + six first_value_as_* (fallback chain), one per State.value_as_* (int, float, bool, str, dict, list). Missing state → None; wrong type → TypeError propagates.

[Copilot]

Pull request overview

Adds typed value getter helpers to the States container to improve ergonomics for consumers that need concrete types without repeated casts/guards, while preserving the existing State.value_as_* mismatch semantics (i.e., TypeError on wrong-typed states; None only for missing/none-typed values).

Changes:

• Add States.get_value_as_{int,float,bool,str,dict,list}() pass-through helpers.
• Add States.first_value_as_{int,float,bool,str,dict,list}() helpers for fallback-chain lookups.
• Add unit tests and documentation examples covering the new typed accessors (including enum keys, missing states, and mismatch behavior).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
pyoverkiz/models.py	Adds the new typed getter methods on States, delegating to State.value_as_*.
tests/test_models.py	Adds coverage for typed getters (hit/miss/NONE/type-mismatch/enum keys/dict+list).
docs/device-control.md	Documents usage examples for typed getters and typed fallback chains.

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