fix: ignore nameof-only token references in CC016 and CC017

[georgepwall1991]

Summary

• ignore token references contained by Roslyn INameOfOperation
• restore CC016 for async methods whose token appears only in nameof
• restore CC017 for BackgroundService loops whose stopping token appears only in nameof
• preserve runtime references in nested lambdas and local functions
• prepare v1.27.177 release metadata

Why

nameof(token) is evaluated at compile time and cannot observe cancellation. The shared reference helper treated it as runtime usage, hiding real ignored-token defects in both rules.

Validation

• two red-first regressions reproduced both false negatives
• focused CC016/CC017 tests: 17 passed
• full suite: 632 passed, 0 failed
• Release build: 0 errors (62 intentional sample analyzer warnings)
• touched-file whitespace verification: clean
• package inspection: both analyzer assemblies present; no NuGet dependencies
• self-review completed as requested; no Claude review used

Tooling note

Slopwatch is required by the local .NET overlay but is not installed on this host; each attempt returned command not found. Manual hygiene and exact-diff review are clean.