featur: Warnings as Errors + Static Analyzers

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DISCLOSURE: LLM-GENERATED TEXT

Landed in PR #57 (session-007): per-assembly csc.rsp (-warnaserror, -warn:4) beside the Runtime, Editor, and Tests.Runtime asmdefs, verified with a deliberate-warning compile-fail drill on Unity 6000.4.6f1; Generator~/Directory.Build.props enables EnableNETAnalyzers with AnalysisMode=All and warnings-as-errors, and the generator-tests lane errors on analyzer diagnostics outside a documented NoWarn contract list. The Unity-free analyzer sweep fixed real culture-sensitivity debt (all CommandArg parsing is invariant-culture now).

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Owner decision: Can we locally enforce popular static analyzers, like ErrorProne.Net and potentially (local) SonarQube? For any 3p packages, we should not check them into source and instead just load them locally on dev-disk.