fix(csharp-tests): remove 10 useless tuple-cast warnings (B-0073 step 2)

[AceHack]

Summary

Step 2 of B-0073. Removes 10 `cs/useless-cast-to-self` warnings flagged by CodeQL on tuple-literal sites in C# tests.

Sites

• `tests/Tests.CSharp/CircuitTests.cs` lines 70-72 (3 casts)
• `tests/Tests.CSharp/ZSetTests.cs` lines 30-31 (4 casts) + 43-45 (3 casts)

Pattern: `((int, long))(N, NL)` → `(N, NL)`. Compiler already infers `(int, long)` from `N` (int) and `NL` (long); the cast was redundant.

Build verification

`dotnet build tests/Tests.CSharp/ -c Release --nologo` returns:

• `0 Warning(s)`
• `0 Error(s)`

Per AGENTS.md `TreatWarningsAsErrors` is on, so 0/0 is the contract.

Composes with

• B-0073 backlog row (full plan; PR backlog(P0): B-0073 LFG csharp Code Scanning cleanup — root-cause of LFG ruleset blocker #95)
• PR fix(codeql): exclude obj/ and bin/ build artifacts from CodeQL (B-0073 step 1) #96 (step 1: obj/bin exclusion in CodeQL config)

After PR #96 + this PR land + forward-sync to LFG + CodeQL re-scan, only the Scorecard SAST meta-finding remains (informational, not a real defect — separate disposition).

Agency-Signature-Version: 1
Agent: otto
Agent-Runtime: claude-code
Agent-Model: claude-opus-4-7
Credential-Identity: AceHack-shared
Credential-Mode: shared-with-aaron
Human-Review: not-implied-by-credential
Human-Review-Evidence: aaron-explicit-ask
Action-Mode: autonomous-fail-open
Task: B-0073-step-2-useless-cast-removal

[Copilot]

Pull request overview

Removes redundant tuple casts in C# test tuple-literal sites to eliminate cs/useless-cast-to-self CodeQL warnings (B-0073 step 2).

Changes:

• Drop ((int, long)) casts around (int, long) tuple literals passed to ZSetModule.ofPairs in C# tests.
• Keep tuple literals as (N, NL) / (1, 3L) etc., relying on C#’s type inference to produce ValueTuple<int, long>.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tests/Tests.CSharp/ZSetTests.cs	Removes redundant tuple casts in ofPairs(new[] { ... }) calls in unit tests.
tests/Tests.CSharp/CircuitTests.cs	Removes redundant tuple casts in ofPairs(new[] { ... }) call in an end-to-end circuit test.