REFACTOR: Improve type hint in generics

[SMoraisAnsys]

Description

As title says, follows #7888.

Issue linked

Related to #5194

Checklist

• I have tested my changes locally.
• I have added necessary documentation or updated existing documentation.
• I have followed the coding style guidelines of this project.
• I have added appropriate tests (unit, integration, system).
• I have reviewed my changes before submitting this pull request.
• I have linked the issue(s) that are solved by the PR if any.
• I have assigned this PR to myself.
• I have added the minimum version decorator to any new backend method implemented.
• I have agreed with the Contributor License Agreement (CLA).

[Copilot]

Pull request overview

This PR refactors several “generic” utilities to improve type-hint accuracy and type-checker compatibility (per #7888 / #5194), adding Protocol-based interfaces for AEDT COM objects and narrowing ambiguous types in common helpers.

Changes:

• Added new AEDT COM Protocol interfaces (_ODesktop, _ODesign) and refined existing Protocol typing (e.g., _OProject.GetTopDesignList).
• Updated get_pyaedt_app and other helpers with safer type narrowing (cast, helper parsing functions) and improved optional typing.
• Refined unit conversion typing/logic in constants.py and adjusted ty exclusions to type-check more of generic/.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/ansys/aedt/core/generic/protocols.py	Adds new Protocols for desktop/design COM objects and tightens a project API return type.
src/ansys/aedt/core/generic/design_types.py	Adds type-narrowing helpers/casts and refines return typing for get_pyaedt_app.
src/ansys/aedt/core/generic/data_handlers.py	Introduces a small helper for regex narrowing and updates type hints for optional args.
src/ansys/aedt/core/generic/constants.py	Adds type aliases/helper for callable unit entries and refactors unit_converter branching.
pyproject.toml	Narrows tool.ty exclusions from the whole generic/ package to a specific file allowlist.
doc/changelog.d/7931.miscellaneous.md	Adds a changelog entry for the generics typing improvements.