fix: unwrap cast receivers in CC027 lifetime analysis

[georgepwall1991]

Verdict

CC027 now diagnoses a returned async call made through an interface or base-type cast of a using-scoped resource; the cast does not extend the resource lifetime.

Evidence

• Red-first regression reproduced the false negative with ((IResource)resource).DoAsync().
• Receiver walking now unwraps CastExpressionSyntax before resolving the using local.
• Direct receiver, using-statement, completed-task argument, alias, and unrelated-task behavior remains green.
• Release build: 62 intentional sample diagnostics, 0 errors.
• Tests: 641 passed, 0 failed.
• Touched-file whitespace verification passed.
• NuGet package v1.27.184 contains both analyzer assemblies and no dependency groups.
• Self-review: no actionable findings.
• Slopwatch was attempted after code changes but is unavailable on this host (command not found).
• Per explicit instruction, no Claude review was used.

Next action

Merge after required CI passes, then publish and verify v1.27.184.

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Do not unwrap user-defined cast conversions

When a using-declared type has a user-defined conversion to another object, unconditionally unwrapping the cast reports CC027 even though the converted object—not the disposable local—is the invocation receiver. For example, return ((Worker)resource).DoAsync(); is safe when an explicit conversion creates an independent Worker, but this walk resolves resource and emits a false positive. Only unwrap identity/reference casts such as the intended base/interface conversions, and stop when the conversion invokes a user-defined operator.

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