Canonical main is red: gating build/test legs fail

[coenttb]

Problem

The latest ci.yml run on canonical main (head 251151cf) concluded run-level failure: https://github.com/swift-foundations/swift-threads/actions/runs/30440801930
Failing legs at that run: Ubuntu (Swift 6.4.x nightly, release), Ubuntu (Swift 6.3, release), swift-format lint, SwiftLint.
The package-owned gating legs among these are: Ubuntu (Swift 6.3, release), swift-format lint, SwiftLint.
On sampled sibling repositories in the same red wave, the stable build/test leg failures reproduce as source-level test defects — e.g. colliding @Suite struct Test declarations introduced by the recent test-suite restructuring/naming sweeps causing invalid redeclaration of 'Test'. Diagnose this repository's own job log first; do not assume the sibling cause.

Proposed outcome

A fresh full-tier workflow_dispatch of .github/workflows/ci.yml at the then-current canonical main head completes with run-level conclusion success, every selected gating leg terminal success, and no failure converted by continue-on-error, an unexplained suppression, or matrix narrowing. Record the passing run URL on this issue before closing.

Repair direction

Read the failing job logs from the linked run, repair the source/test defects in this repository (test-suite naming collisions, compile errors, or genuine test failures), and leave CI configuration untouched. If a failure reproduces only as a compiler crash or SDK defect, it is centrally owned — report it on this issue instead of working around it.

Additional context

Out of scope (centrally owned, do not mask or 'fix' locally): advisory Ubuntu nightly legs (Swift 6.4.x/main nightly — owned with the Swift 6.4 baseline work, swift-institute/.github#95), Ubuntu (Swift 6.3, Embedded Wasm SDK build) failures matching the swift-frontend signal-11 crash, Ubuntu (Swift 6.3, Android SDK build) failures from semaphore.h missing in the Android SDK artifactbundle, and Static Linux musl failures pending central diagnosis. Do not add continue-on-error, narrow the matrix, or edit workflow files to reach green; the caller/wrapper/universal chain is owned centrally.

Part of the CI-green wave under Goal swift-institute/.github#94; lint-rule (swift-linter) convergence remains owned by Goal swift-institute/.github#90 and is not in this issue's scope.

[coenttb]

Verified: latest canonical-main run is still red, but the failure is a dependency-owned defect, not package red — the gating Linux build leg fails compiling Linux Kernel IO Uring Standard (owned by swift-linux, target Linux Kernel IO Uring Standard): IORING_FIXED_FD_NO_CLOEXEC (and related io_uring constants) is not found in scope on this runner's kernel/glibc headers. No mechanical lint/format/build fix in this repo can address it — the fix belongs in swift-linux's io_uring constant availability guards. Rerunning the failed run and moving on per the dependency-stale-red playbook; exact owner: swift-foundations/swift-linux.

[coenttb]

Fixed the gating swift-format (RemoveLine, 2 sites) and SwiftLint (vertical_whitespace_between_cases, 2 sites) findings in Kernel.Thread.Pool.Lifecycle.swift, Kernel.Thread.Pool+Run.swift, and Kernel.Thread.Pool Tests.swift. Pushed 19df7ea.

Left the 3x no_any_protocol_existential SwiftLint findings untouched — replacing an any <Protocol> existential with a generic/typed-throws constraint per [API-ERR-006] is an API/design decision, not mechanical, so not attempting it here.

The Linux build legs remain separately red on the dependency-owned Linux Kernel IO Uring Standard defect noted above (owned by swift-linux).

Fresh run: https://github.com/swift-foundations/swift-threads/actions/runs/30560673933

Leaving open — format/lint should improve; the existential question and the io_uring dependency fix are still outstanding.