ci: wire dotnet test into build workflow

[rubenhensen]

Closes #10.

The test project (61 tests covering BuildPolicyJson, CryptifyClient, PkgClient, ZipHelper, and ClientVersion) was merged in #36, but the CI workflow was never updated to actually run them. The job is even named "Build and test" — this makes it true.

One-line change: adds a Test step between Build and Pack (dry run), using --no-build to reuse the already-built output. Both SDK versions (8.0.x and 10.0.x) are already installed by setup-dotnet, so dotnet test exercises both target frameworks automatically.

[dobby-coder]

On it, @rubenhensen! I'm reviewing your PR now and will post a consolidated review with my findings shortly.

[dobby-coder]

Approving — clean, correct one-line CI change.

The Test step is placed between Build and Pack (dry run) and uses --no-build to reuse the Release build. The slnx build produces test DLLs for both target frameworks, so --no-build is satisfied, and since setup-dotnet installs both 8.0.x and 10.0.x, dotnet test exercises net8.0 and net10.0 automatically. The job named "Build and test" now actually tests.

Verification: built the solution and ran the exact PR command locally — 61/61 tests pass on net10.0. net8.0 only fails locally for lack of that runtime (workspace ships net10 SDK only); CI installs 8.0.x so it runs there. Title is conventional-commit format. No rule findings, no review findings.

[dobby-coder]

Approved! ✅ Ran a full compliance check — no issues found. Built the solution locally and all 61/61 tests pass on net10.0; net8.0 is deferred to CI since that runtime isn't in my workspace, but the workflow you've wired up will cover it there.

Clean, minimal change. Good to merge.