domain: release server id by revoke etcd session

[AmoebaProtozoa]

What problem does this PR solve?

Issue Number: close #64191

Problem Summary:

What changed and how does it work?

change the way server id was released. Instead of deleting the etcd key directly, which may leak empty lease, close the serverID session instead.

Check List

Tests

• Manual test (add detailed scripts or steps below)

• tiup playground with local build tiup playground --db.binpath ./bin/tidb-server
• check server id and lease

# log
[2025/10/30 15:46:46.044 +08:00] [INFO] [domain.go:2678] [acquireServerID] [serverID=1989] ["lease id"=22319a34154c819a]`

# etcdctl
❯ etcdctl --endpoints 127.0.0.1:2379 get "/tidb/server_id/1989" --prefix -w fields
"ClusterID" : 15674009460217235928
"MemberID" : 3474484975246189105
"Revision" : 298
"RaftTerm" : 2
"Key" : "/tidb/server_id/1989"
"CreateRevision" : 207
"ModRevision" : 207
"Version" : 1
"Value" : "0"
"Lease" : 2463920019634684314
"More" : false
"Count" : 1
❯ etcdctl --endpoints 127.0.0.1:2379 lease timetolive 22319a34154c819a
lease 22319a34154c819a granted with TTL(43200s), remaining(43011s)

• scale-in tidb tiup playground --pid xxx
• check key and lease removed

# log
[2025/10/30 15:51:10.393 +08:00] [INFO] [domain.go:2703] ["releaseServerID succeed"] [serverID=1989] [leaseID=2463920019634684314]

# etcdctl
❯ etcdctl --endpoints 127.0.0.1:2379 get "/tidb/server_id/1989" --prefix -w fields
"ClusterID" : 15674009460217235928
"MemberID" : 3474484975246189105
"Revision" : 366
"RaftTerm" : 2
"More" : false
"Count" : 0
❯ etcdctl --endpoints 127.0.0.1:2379 lease timetolive 22319a34154c819a
lease 22319a34154c819a already expired

Release note

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None

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[codecov]

Codecov Report

❌ Patch coverage is 50.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.8469%. Comparing base (0230916) to head (8a38ec6).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@               Coverage Diff                @@
##             master     #64192        +/-   ##
================================================
+ Coverage   72.6828%   74.8469%   +2.1640%     
================================================
  Files          1858       1881        +23     
  Lines        502725     510840      +8115     
================================================
+ Hits         365395     382348     +16953     
+ Misses       115087     104881     -10206     
- Partials      22243      23611      +1368     

Flag	Coverage Δ
integration	48.1411% <0.0000%> (?)
unit	72.5232% <50.0000%> (+0.2767%)	⬆️

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Components	Coverage Δ
dumpling	52.8700% <ø> (ø)
parser	∅ <ø> (∅)
br	62.2434% <ø> (+15.9062%)	⬆️

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[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: disksing, hawkingrei
Once this PR has been reviewed and has the lgtm label, please assign wjhuang2016 for approval. For more information see the Code Review Process.
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Needs approval from an approver in each of these files:

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[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-10-30 07:58:33.163479679 +0000 UTC m=+1549819.240732239: ☑️ agreed by hawkingrei.
• 2025-10-30 08:20:10.267672507 +0000 UTC m=+1551116.344925057: ☑️ agreed by disksing.

[AmoebaProtozoa]

/assign @wjhuang2016