docs: document Region and maintenance events

[WenyXu]

What changed

• add Region events and Maintenance events guides for Metasrv event records in distributed deployments
• document repartition, repartition_group, Region migration, GC, and Remote WAL pruning with read-only SQL queries and sample results
• explain Region ID components, source-to-target Region mappings, GC report file lists, and Remote WAL pruning boundaries
• add English and Chinese navigation links for the new guides
• keep unrelated existing Events pages unchanged; also align the Chinese recent-events wording in Nightly and 1.2

Part of #2723

Scope

• Documentation versions: Nightly and 1.2
• Languages: English and Chinese

Verification

• git diff --check
• Read-only MySQL queries against local GreptimeDB on port 4002 for the documented repartition, Region migration, GC, and Remote WAL queries
• Manual review against the event recorder source and Grafana Events dashboard

Checklist

• I verified the content against the applicable GreptimeDB version.
• I updated the relevant documentation versions and languages, or explained why not.
• I checked changed links and anchors.
• I updated navigation when the document structure changed.

[Copilot]

Pull request overview

Adds Nightly English and Chinese documentation for Metasrv-emitted operational event families (repartitioning, region migration, batch GC, and WAL pruning) so operators can query greptime_private.events for distributed-cluster maintenance and region-level activity.

Changes:

• Add new “Region events” and “Maintenance events” pages with SQL query examples and field interpretation notes.
• Extend Events overview pages to link to the new focused guides.
• Update sidebar navigation to include the new pages under Monitoring → Events.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
sidebars.ts	Adds the new Events subpages to the Monitoring navigation.
docs/user-guide/deployments-administration/monitoring/events/overview.md	Links to the new Region/Maintenance events guides from the English Events overview.
docs/user-guide/deployments-administration/monitoring/events/region-events.md	New English guide for repartition and region migration events, with SQL cookbook examples.
docs/user-guide/deployments-administration/monitoring/events/maintenance-events.md	New English guide for batch GC and WAL prune events, including behavior notes and example outputs.
i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/monitoring/events/overview.md	Links to the new Region/Maintenance events guides from the Chinese Events overview.
i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/monitoring/events/region-events.md	New Chinese guide for repartition and region migration events, with SQL cookbook examples.
i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/monitoring/events/maintenance-events.md	New Chinese guide for batch GC and WAL prune events, including behavior notes and example outputs.

Suppressed comments (2)

docs/user-guide/deployments-administration/monitoring/events/region-events.md:91

• The sample output includes concrete peer addresses (e.g., 172.16.x.x:4001). If the query is adjusted to omit peer addresses, the example output should also remove the *_datanode_addr columns to avoid publishing internal IPs/ports.

+-------------------------------+--------------------------------------+-----------------+---------------+----------+---------------+---------------------------------+--------------------+----------------------+--------------------+----------------------+
| timestamp                     | procedure_id                         | procedure_state | region_id     | table_id | region_number | region_migration_trigger_reason | source_datanode_id | source_datanode_addr | target_datanode_id | target_datanode_addr |
+-------------------------------+--------------------------------------+-----------------+---------------+----------+---------------+---------------------------------+--------------------+----------------------+--------------------+----------------------+
| 2026-08-10 02:52:50.078350103 | 63167e21-0165-4964-afef-02271baa126b | Done            | 5162550689808 |     1202 |            16 | AutoRebalance                   |                  1 | 172.16.62.49:4001    |                  2 | 172.16.232.158:4001  |
+-------------------------------+--------------------------------------+-----------------+---------------+----------+---------------+---------------------------------+--------------------+----------------------+--------------------+----------------------+

i18n/zh/docusaurus-plugin-content-docs/current/user-guide/deployments-administration/monitoring/events/region-events.md:91

• 示例输出包含具体的 peer 地址（如 172.16.x.x:4001）。如果查询改为不返回 peer 地址，示例输出也应移除 *_datanode_addr 列，避免在文档中发布内部 IP/端口。

+-------------------------------+--------------------------------------+-----------------+---------------+----------+---------------+---------------------------------+--------------------+----------------------+--------------------+----------------------+
| timestamp                     | procedure_id                         | procedure_state | region_id     | table_id | region_number | region_migration_trigger_reason | source_datanode_id | source_datanode_addr | target_datanode_id | target_datanode_addr |
+-------------------------------+--------------------------------------+-----------------+---------------+----------+---------------+---------------------------------+--------------------+----------------------+--------------------+----------------------+
| 2026-08-10 02:52:50.078350103 | 63167e21-0165-4964-afef-02271baa126b | Done            | 5162550689808 |     1202 |            16 | AutoRebalance                   |                  1 | 172.16.62.49:4001    |                  2 | 172.16.232.158:4001  |
+-------------------------------+--------------------------------------+-----------------+---------------+----------+---------------+---------------------------------+--------------------+----------------------+--------------------+----------------------+

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[WenyXu]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: 6d535fab2c

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[fengjiachun]

LGTM