Windows claim stress test can read an incomplete claim record

[janicduplessis]

Problem

The blocking Windows unit lane can refuse a claim during the real-process stress test, even though the test expects all processes to cycle the same claim set without overlap or a refusal.

Evidence

• PR #942 CI run 35552971373, attempt 1 failed packages/stim-cli/src/__tests__/ownership-claim.test.ts at line 569 in many processes cycling the same claim set never overlap and never surface a raw errno.
• At iteration 15, one child returned STIM_CLAIM_REFUSED for build.lock/shared/<token>.claim because its record is missing, truncated or not valid JSON. The same test passed on this PR's Node 22 and Node 24 lanes, and the PR changes only website/docusaurus.config.ts.
• A previous intermittent failure of this test was tracked in Windows claim stress test still refuses once in a while after #913 #925 and closed after a different mitigation; that issue did not identify this record-read reason.

Cause

Unknown. Determine whether a Windows reader can observe the claim before its record is fully published, or whether this is a transient read/delete state that should be retried while preserving the ownership safety rules.

Fix idea

Reproduce the exact refusal on windows-latest, trace the record publish/read path, and fix the race without allowing a second owner. Verify repeated real-process stress runs and the full blocking Windows unit lane.