fix(lock): stop renewing a lease that cannot be extended

[MontaGhanmy]

Summary

• Return Redis renewal errors and an internal errLockLost from Extend() instead of discarding the result. Log the first failed renewal and stop further renewal attempts.
• Example: process A acquires a 20-second lease, then pauses before its first renewal. The lease expires at 20 seconds and process B acquires the same lock at 21 seconds with a new token. When A resumes at 25 seconds, Redis rejects A's old token. Previously A kept trying every tick; now the renewer logs the failure and exits.
• Stopping renewal does not cancel the protected operation. RAG workspace creation and Swift migration can still continue after losing their lease.
• Temporary Redis errors also stop renewal in this change. For example, if a renewal fails at about 6.7 seconds and Redis recovers at 8 seconds, no retry occurs at about 13.3 seconds and the original lease expires at 20 seconds. Recovery from transient errors remains a limitation.