Bumps ktsu.RoundTripStringJsonConverter from 1.0.56 to 1.0.57

---
updated-dependencies:
- dependency-name: ktsu.RoundTripStringJsonConverter
  dependency-version: 1.0.57
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: ktsu
...

Signed-off-by: dependabot[bot] <support@github.com>

Bump the ktsu group with 1 update

---
updated-dependencies:
- dependency-name: Polyfill
  dependency-version: 11.3.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Bump Polyfill from 11.2.0 to 11.3.0

Every ktsu .NET repository carried its own copy of dotnet.yml and they had
drifted into five different files. This replaces the local copy with one
canonical workflow that is byte-identical in every repository, folding in the
drift rather than flattening it.

The drift, and where it went:

* macOS is back in the test matrix. It had been excluded org-wide because a
  macOS runner widened one repository's target frameworks to include a
  net10.0-ios head needing a workload this job does not install. That widening
  is now opt-in, so every other repository stops paying for it. UI test
  projects still run on Linux only, so a macOS cell stays cheap.
* The UI-test rule is now "Linux runs them, every other platform does not",
  rather than naming Windows, so a platform added later gets the cheap
  treatment by default instead of silently inheriting the expensive one.
* The Linux coverage report's paths are rewritten to this job's workspace
  before analysis. Sonar matches coverage to source by path, so a Linux-only
  suite's coverage was being dropped without a word. The step no-ops where
  there is no Linux report.
* The test and release jobs install the 8.0 and 9.0 runtimes alongside the
  pinned SDK, because test projects commonly multi-target every framework
  their library publishes and the test host needs those runtimes present.
  global.json still pins the SDK, so this only adds runtimes.
* Coverage exclusions are extensible per repository through the
  SONAR_COVERAGE_EXCLUSIONS_EXTRA variable, so a repository with a file that
  cannot be executed rather than one nobody has tested yet can say so without
  editing this file and making every other repository carry its paths.
* A SonarQube Cloud outage skips analysis instead of failing the build, and is
  never dressed up as a pass. Where the gate is blocking, an outage still fails.
* Stale comments explaining one repository's circumstances are rewritten to
  explain the shared rule, with the measurements kept and attributed.

Nothing in the pipeline's shape changed: the same jobs, the same steps, the
same order.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015qxqZVzN8CJcDxTb5gtWua