chore: advance main development identity to 0.5.0-rc.2

[mksolutionsuniversal]

Summary

Advance the post-release main development identity to 0.5.0-rc.2 so source builds after the frozen published v0.5.0-rc.1 checkpoint cannot be confused with that release artifact.

Scope

• change <Version> / <InformationalVersion> from 0.5.0-rc.1 to 0.5.0-rc.2,
• keep AssemblyVersion / FileVersion at 0.5.0.0,
• update the exact application-version test,
• document the distinction between published v0.5.0-rc.1 and the current main development target,
• record the development identity in [Unreleased].

Important release boundary

• 0.5.0-rc.2 is a development target only.
• Do not create a tag or GitHub Release for v0.5.0-rc.2 as part of this PR.
• Published stable v0.4.0 remains untouched.
• Published pre-release v0.5.0-rc.1 remains untouched and immutable.

Hardware impact

None. No C# runtime hardware-control code, SMC write path, power-management implementation, driver code, workflow logic, or packaging script is changed.

Expected qualification remains the current 589/589 automated-test baseline plus existing release-packaging validation.

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