Disable iOS LibraryMode tests by design, drop tracking-issue reference

[Copilot]

The iOS.Device/Simulator.LibraryMode.Test projects were excluded from Apple-mobile runs against a tracking issue that is now being closed. Per reviewer feedback, an exclusion should either be fixed, deleted, or marked "by design" without an ActiveIssue reference.

Changes

• src/libraries/tests.proj: Replaced the <!-- Tracking issue: ... --> comment above the two LibraryMode ProjectExclusions with a by-design comment, matching the convention used by other permanent exclusions in this file (e.g. <!-- PNSE -->).

<!-- Library mode is not supported on Apple mobile; excluded by design. Use RunDisablediOSTests=true to run locally. -->
<ProjectExclusions Include="$(RepoRoot)/src/tests/FunctionalTests/iOS/Device/LibraryMode/iOS.Device.LibraryMode.Test.csproj" />
<ProjectExclusions Include="$(RepoRoot)/src/tests/FunctionalTests/iOS/Simulator/LibraryMode/iOS.Simulator.LibraryMode.Test.csproj" />

Notes

• The exclusion items are unchanged: tests remain off by default for Apple mobile and can still be run locally with RunDisablediOSTests=true.
• This was the only genuine in-repo reference to the issue; the other grep hit (SlhDsaTestData.cs) is a coincidental hex substring in test-vector data.

• Fixes iOS.Device/Simulator.LibraryMode.Test: failed to determine exit code - RETURN_CODE_NOT_SET #116558

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Copilot's findings

• Files reviewed: 1/1 changed files
• Comments generated: 1

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Copilot's findings

Comments suppressed due to low confidence (1)

src/libraries/tests.proj:317

• The updated comment doesn't match the PR description (it omits both the explicit "excluded by design" rationale and the hint for running these tests locally). Consider updating the comment so the intent and local opt-in mechanism are clear and consistent with the PR narrative.

    <!-- Library mode is not supported on Apple mobile -->

• Files reviewed: 1/1 changed files
• Comments generated: 0 new

[jkoritzinsky]

If LibraryMode is not supported and will not be supported, can we just delete the tests instead of carrying around always-disabled tests?

[steveisok]

Library mode for mobile is basically NativeAOT deployed as a shared library. I think it still has value for mobile targets, but I doubt we really need the functional tests.

[akoeplinger]

what prevents us from fixing the tests so they actually work?

[akoeplinger]

I agree that we should delete them instead of disabling