ci(windows): raise coverage test timeout to 60s

After the 4-partition split, other PRs' windows coverage now fails on
process-bound subagent-acp tests timing out at 30s under self-hosted
concurrency. Give the coverage lane the same 60s per-test budget that the
earlier failover profile used.

.github/workflows/ci.yml

@@ -446,7 +446,7 @@ jobs:
     env:
       DSH_COVERAGE_MAX_WORKERS: '6'
       DSH_COVERAGE_PARTITIONS: '4'
-      DSH_COVERAGE_TEST_TIMEOUT_MS: '30000'
+      DSH_COVERAGE_TEST_TIMEOUT_MS: '60000'
       DSH_GATE_CONCURRENCY: '3'
     steps:
       - uses: actions/checkout@v6