Flaky-run counts now count only actual failing runs

Flaky-test detection now flags only the failing run as flaky when a test case both passes and fails on the same commit and scheme. Previously, every run in that group (including the passing ones) was counted as flaky, which inflated flaky-run counts and could cause auto-quarantine rules to trigger too quickly. The flaky-run count, flakiness rate, and dashboard numbers now reflect only the spurious failures. The Flaky Runs tab, single run view, and PR comment views still show the full pass/fail breakdown for each flaky commit.