fix(test): end the CI unit-test hang by making Turbine buffer emissions

[fardavide]

Fixes the "test-process hang" that survived #17 and is currently keeping main red: the unit-test job dies ~90s into the run with exit code 1 and no test summary, on both PR and push runs.

Root cause

Turbine.expectInitial recursed on unchanged state whenever the current value equaled the expected one. That recursion has no suspension point, so the task never yields: it pins a cooperative-pool thread and allocates async frames without bound until a different value happens to arrive.

• Locally (many cores) the view model's next emission lands in milliseconds on a spare pool thread and breaks the spin — tests pass, nobody notices.
• On the 3–4-core CI runner all eight turbine tests spin concurrently, occupy the entire cooperative pool, and starve the very load() work that would produce the interrupting emissions. The process stalls, memory grows, and it dies without reporting — taking the unrelated suites down with it.

Fix

RealTurbine is rebuilt on an AsyncStream: every emission is buffered and consumed oldest-first, and waiting is a genuine suspension (iterator.next(isolation:)), so the pool is never touched. expectInitial keeps its contract — consume the initial value if the subscription caught it, or put the first value back for value() if the view model progressed before we subscribed. Verified against every call site that the FIFO semantics return exactly what the old latest-only code returned (each observed field is emitted once per load/send, with removeDuplicates upstream).

Two Swift 6 strict-concurrency requirements shaped the implementation: the protocol's associatedtype Value must be Sendable (values hop into the MainActor-isolated witness), and the stream iterator is advanced via a local copy with next(isolation: #isolation) (SE-0421), since a mutating async call on an isolated stored property — or a plain nonisolated next() — is rejected.

Also in this PR

• TurbineTests (new, in the previously empty TestTests target): 4 regression tests; the first is the minimal reproduction that spins forever under the old code.
• .github/rulesets/protect-main.json: importable branch ruleset requiring all four CI checks on main with an empty bypass list. Creating rulesets needs repo-admin, so apply it via Settings → Rules → New ruleset → Import a ruleset, or gh api repos/fardavide/Swiftly/rulesets --method POST --input .github/rulesets/protect-main.json.
• ci.yml is net-unchanged: an aggregate "CI passed" gate job was added and later removed in favor of requiring the four job checks directly.

Verification

Full CI dispatched on this branch: run 30963134024 — all jobs green. The unit-test step completes in 82s with a full summary, where it previously died at ~90s.

Merging this turns main green again.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Myrncy7JAwkAjnfT8jm2h6

[semanticdiff-com]

Review changes with  

Changed Files

File	Status
SwiftlyCore/Sources/Common/Test/Turbine.swift	11% smaller
.github/rulesets/protect-main.json	0% smaller
SwiftlyCore/Tests/Common/TestTests/TurbineTests.swift	0% smaller