fix(state): acquireStateLock throws on non-EEXIST openSync errors (#3773)

* fix(state): acquireStateLock throws on non-EEXIST openSync errors

Closes #3772

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore(changeset): update pr reference to #3773

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(state): retry on EPERM/EBUSY in acquireStateLock and withPlanningLock

Resolves state update TOCTOU failure on macos-22 and config-set
concurrency failure on windows-24.
Root cause: openSync(O_CREAT|O_EXCL) can return EPERM or EBUSY
transiently on some CI OS+AV combinations when the lock file is
briefly held open by the deleting process; the new throw-on-non-EEXIST
guard from #3772 propagated these transient errors, killing child
processes and causing lost updates in the concurrency tests.
Fix: guard EPERM/EBUSY with an explicit continue before the
throw-on-non-EEXIST line in both acquireStateLock and withPlanningLock;
the C1 source-audit test still passes because the throw pattern is
preserved for all other non-EEXIST codes.

Refs #3772

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>