sonar(S3358): Ternary operators should not be nested [src/Equiv.Frontend.CSharp/, 5 findings]

[github-actions]

Filed by tools/sonar-triage/sonar-triage.ps1. This issue is the ticket: see docs/adr/0016-sonar-issue-triage.md.

Goal

One part of the rule:csharpsquid:S3358 batch, which is too big for one PR. Clear the
5 findings below, across 2 files under src/Equiv.Frontend.CSharp/. The parent issue
(shown by GitHub above this one) holds the rule-wide decision: follow it, and match the shape
of fix that already-merged parts used.

• In SonarCloud: https://sonarcloud.io/project/issues?id=Zafnok_code-equivalency&rules=csharpsquid%3AS3358&resolved=false
• Rule description: https://rules.sonarsource.com/csharp/RSPEC-3358/

Findings

Location	Rule	Message	Sonar
src/Equiv.Frontend.CSharp/Execution/ProbeArguments.cs:84	csharpsquid:S3358	Extract this nested ternary operation into an independent statement.	open
src/Equiv.Frontend.CSharp/Execution/ProbeArguments.cs:90	csharpsquid:S3358	Extract this nested ternary operation into an independent statement.	open
src/Equiv.Frontend.CSharp/Execution/ProbeArguments.cs:91	csharpsquid:S3358	Extract this nested ternary operation into an independent statement.	open
src/Equiv.Frontend.CSharp/Execution/ProbeArguments.cs:92	csharpsquid:S3358	Extract this nested ternary operation into an independent statement.	open
src/Equiv.Frontend.CSharp/Fingerprinting/BoundSerialiser.cs:303	csharpsquid:S3358	Extract this nested ternary operation into an independent statement.	open

Acceptance criteria

1. Every finding above is either fixed, or added to tools/sonar-triage/policy.jsonc with
   verdict: accept and a reason citing an ADR or a ticket. A finding that no longer
   reproduces on HEAD is called out in the PR body, not silently dropped.
2. ./build.ps1 -Integration is green.
3. No #pragma warning disable, no coverage exclusion, no gate lowered.

How to fix

Point a session at this issue and say use equiv-sonar-fix.