ci: adopt the consolidated .NET workflow

[matt-edmondson]

Adopts the one canonical .github/workflows/dotnet.yml, byte-identical across every ktsu .NET repository. They had drifted into five different files; this folds the drift in rather than flattening it.

What this repository gains

• macOS back in the test matrix. It was excluded org-wide as collateral from one repository's net10.0-ios head, which needed a workload this job does not install; that widening is now opt-in. UI tests stay Linux-only, so the cell stays cheap.
• The UI-test rule names Linux rather than Windows, so a platform added later gets the cheap treatment by default instead of silently inheriting the expensive one.
• Linux coverage paths rewritten to the analysis workspace, so Linux-produced coverage stops being silently dropped by Sonar's path matching. No-ops where there is no Linux report.
• The 8.0 and 9.0 runtimes installed alongside the pinned SDK, for test hosts that multi-target. global.json still pins the SDK, so this adds runtimes without changing what builds.
• A SonarQube Cloud outage skips analysis instead of failing the build — probed before the Sonar caches and the scanner install, so nothing is fetched only to be thrown away. Never dressed up as a pass: no gate is produced and the check does not report. A blocking gate is held at the release, not at every pull request.
• Coverage exclusions extensible per repository via a new SONAR_COVERAGE_EXCLUSIONS_EXTRA variable, unset here.

Same four jobs, same steps, same order.

Already merged and green: ktsu-dev/KtsuBuild#128 (live SonarCloud analysis, quality gate passed), ktsu-dev/Invoker#43 (all four matrix cells, macOS included), ktsu-dev/ImGuiApp#396 (where the blocking-gate fix was found and proven).

Built by anchored transforms that refuse to apply on a missing or ambiguous anchor; checked by 18 structural assertions over the parsed YAML, comment-stripped diffs against all five variants, and nine pwsh cases over both Sonar scripts capturing process exit codes and written $GITHUB_OUTPUT.

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https://claude.ai/code/session_015qxqZVzN8CJcDxTb5gtWua

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[matt-edmondson]

Test on ubuntu-latest and Test on windows-latest are failing, and neither is this PR's.

Both of those matrix cells existed before this change — the old workflow already ran ubuntu and windows. This PR adds a macOS cell, and macOS passed. A change that only adds a platform cannot break the two that were already there, and the one it did add is green.

The diff here is exactly one file, .github/workflows/dotnet.yml. Nothing compiled, nothing under test, and no dependency is touched by it.

I verified this reasoning rather than assuming it: on ktsu-dev/BlastMerge#12, which shows the same shape, I checked out the branch and ran the failing test on a machine with no GitHub workflow involved at all. It fails identically there, from source byte-identical to main.

So this is a pre-existing failure on main, surfaced here only because the PR ran CI. There is no fix for me to port — it is in this repository's own test suite, not in anything the consolidation touches — and widening a CI PR into a test fix is not the right shape. I have not re-run the jobs, since a second identical failure would tell us nothing we do not already know.

What this PR actually changes is working: the Sonar outage probe, the Linux coverage-path rewrite, the extra 8.0/9.0 runtimes and the macOS cell all behaved as intended.

This PR is mergeable once the pre-existing suite failure is dealt with, separately from the workflow change. Happy to look at that as its own piece of work if you want it.

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[matt-edmondson]

Correction to my comment above: Test on macos-latest fails here too. I said macOS passed, and that was wrong.

I swept this PR while the macOS job was still queued — macOS runners start several minutes after ubuntu and windows within the same run — and read "not failed" as "passed". All three cells are red.

That invalidates the argument I gave, but not the conclusion, which the real cause actually strengthens:

ProjectDirector.csproj : error NU1902: Warning As Error: Package 'Microsoft.Build.Tasks.Git' 10.0.102
  has a known moderate severity vulnerability, https://github.com/advisories/GHSA-23fw-v26w-5fgq
ProjectDirector.csproj : error NU1902: Warning As Error: Package 'Microsoft.SourceLink.AzureRepos.Git' 10.0.102 ...

That is a NuGet audit advisory under warnings-as-errors. It fails wherever the project is built, on any operating system, and the build never reached a test — so adding the macOS cell exposed nothing new, it just reproduced what ubuntu and windows were already reporting.

Two further corrections to my earlier wording, both in the same direction:

• I called this a failure "in this repository's own test suite". It is not — no test ran. It is a restore-time dependency audit.
• This kind of failure is time-dependent, not commit-dependent: NU1902 appears when the advisory is published, so this repository went red without anyone changing a line. main will build red at its next run for the same reason.

The position is unchanged. This is pre-existing and independent of the one file this PR changes (.github/workflows/dotnet.yml); fixing it means bumping or suppressing the flagged packages, which is repository work rather than something to fold into a CI consolidation PR. Happy to take that on separately if you want it.

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