fix: detect implicit await forms in CC019 cancellation catches

[georgepwall1991]

Summary

• teach CC019 to recognize await foreach
• recognize both await using var and await using (...)
• preserve the current-function boundary added in v1.27.174
• update release metadata and analyzer-health evidence for v1.27.175

Why

These constructs carry their await keyword on statement syntax instead of producing an AwaitExpressionSyntax. Broad catches around async enumeration or async disposal could therefore swallow OperationCanceledException without a CC019 diagnostic.

Validation

• red-first tests reproduced all three false negatives
• focused CC019 tests: 13 passed
• full suite: 629 passed, 0 failed
• Release build: 0 errors (62 intentional sample analyzer warnings)
• package inspection: analyzer and code-fix DLLs present; no NuGet dependencies
• format verification completed
• self-review completed as explicitly requested; no Claude review used

Release

Prepared as v1.27.175.