* ci: split mac/windows/qcom-cl tests into platform.yml
Move the 6 jobs that don't run on Linux (4 macos, 1 windows, 1 QCOM CL
compile test on arm) out of test.yml into a separate Platform Tests
workflow so they run (and can be gated/runners-matched) independently.
* ci: gate platform tests to the upstream repo
Skip mac/windows/qcom-cl jobs anywhere but tinygrad/tinygrad, so the
Platform Tests workflow is disabled on the gitea fork (and any fork).
* ci: revert repo gate on platform tests
Job-level if is only evaluated by gitea when a runner with matching
labels fetches the task; with no mac/windows/arm runners the jobs queue
forever. Disable the workflow on the instance instead.
