i18n(ja): fix translation defects in the v8.1.0, v8.1.2, and v8.2.0 release notes

[yahonda]

What is changed, added or deleted? (Required)

Fixes translation defects in the Japanese release notes for v8.1.0, v8.1.2, and v8.2.0. This is round 2 of the releases/ review; round 1 is #24143. I checked each item against its EN bullet (release-8.5).

Meaning fixes

• Swapped identifiers, mostly in 8.2.0:
  • CHECK constraint vs JSON_SCHEMA_VALID().
  • ANALYZE vs scan.
  • tidb_persist_analyze_options = OFF vs tidb_enable_column_tracking.
  • TABLESAMPLE vs plan not supported.
  • tidb_enable_async_merge_global_stats vs Distinct_count.
  • Table vs field for INFORMATION_SCHEMA.PARTITIONS/TABLES/KEY_COLUMN_USAGE.
• Scrambled sentences:
  • 8.2.0 Syncpoint: two EN sentences were merged, and "Starting from v8.2.0" was dropped.
  • 8.2.0 PREDICATE COLUMNS.
  • 8.1.0 ADD COLUMN.
  • 8.1.0 TABLESAMPLE with static prune mode.
• Other meaning changes:
  • "compatibility testing for log backup and adding index acceleration" (8.1.0).
  • "the Leader fails to transfer" (8.1.0).
  • The replication latency of TiCDC and PITR (8.1.2).
  • "released" in the sense of freed (8.1.2).
  • Upgrading the k8s.io/api library version (8.1.2).
  • "(32-bit platform)" and "from" were dropped (8.2.0).
  • A description had become an instruction to the reader (8.2.0).
  • "at the source" and "identification phase" (8.1.0).
• Wrong-domain words:
  • 関数 → 機能 for "functions".
  • リージョン結合 → リージョンマージ.
  • 列剪定 → 列プルーニング.
  • 早期応募 → 早期適用.
  • 粗視化リージョン散乱 → 粗粒度リージョン分散.
  • やり直し → REDO.
  • 古い読み取り → ステイル読み取り (glossary).

Literals restored

• Grafana panel and metric names:
  • Compaction Job Size(files)
  • Raft dropped messages
  • gRPC request sources duration
  • Kafka Outgoing Bytes
  • Ownership history
• Connection Count.
• The contributor link text @[hi-rustin], as in EN.
• >.
• The handle/issue order.
• Missing spaces between handles.

Other fixes:

• About 20 dropped は/を/が/の after backticks and links.
• Untranslated "Security" and "log".
• A plain-form ending.

The 発売日 → リリース日 lines are not touched here; they are in #24146. The rendering of "disaggregated storage and compute" as 分散ストレージおよびコンピューティング (39 occurrences across the corpus) is also left for a separate term decision.

EN-side candidate, not changed: 8.1.0 "a union clustered index" probably means "composite clustered index".

Which TiDB version(s) do your changes apply to? (Required)

Tips for choosing the affected version(s):

By default, CHOOSE MASTER ONLY so your changes will be applied to the next TiDB major or minor releases. If your PR involves a product feature behavior change or a compatibility change, CHOOSE THE AFFECTED RELEASE BRANCH(ES) AND MASTER.

For details, see tips for choosing the affected versions.

• i18n-ja-release-8.5 (TiDB Japanese documentation for TiDB 8.5 versions)

What is the related PR or file link(s)?

• This PR is translated from:
• Other reference link(s): i18n(ja): fix translation defects in the v8.5.x release notes #24143, i18n(ja): use the glossary rendering for Release date in the release notes #24146

AI agent involvement

• The changes in this PR were primarily made by an AI agent on behalf of the PR author.

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

🤖 Generated with Claude Code

Summary by CodeRabbit

• Documentation
  • Clarified compatibility notes for TiDB Lightning, TiDB failover IDs, and TiCDC event handling.
  • Specified conditions for JSON_SCHEMA_VALID() checks, TiCDC sync points, backup restoration, and configuration limits.
  • Updated descriptions of release features, improvements, deprecations, and bug fixes across the 8.1.0, 8.1.2, and 8.2.0 release notes.

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📥 Commits

Reviewing files that changed from the base of the PR and between aef06ad and 7e0b5f4.

📒 Files selected for processing (3)

• releases/release-8.1.0.md
• releases/release-8.1.2.md
• releases/release-8.2.0.md

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📝 Walkthrough

Walkthrough

Release notes for versions 8.1.0, 8.1.2, and 8.2.0 receive wording revisions and clarifications to selected technical conditions, labels, and attributions. The described features, improvements, and fixes otherwise remain unchanged.

Changes

Release note updates

Layer / File(s)	Summary
Release-note wording and clarifications releases/release-8.1.0.md, releases/release-8.1.2.md, releases/release-8.2.0.md	The release notes correct wording, labels, and attributions. They clarify selected compatibility, configuration, and bug-fix descriptions without changing the listed features, improvements, or fixes.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Other

Merge Risk: ⚪ Minimal · up to 7e0b5

The checked release-note corrections preserve the documented behavior and compatibility conditions. No concrete merge-blocking risk remains.

Architecture Summary

Architecture risk: 🔵 Low · up to 7e0b5

The change affects 1 system.

Changed systems: releases

Architecture concerns
No architecture-level concerns identified.

Review details

Systems and components

• observed — releases (service) was modified; 3 changed files map to changed impact.

Before / after behavior

• observed — Modified behavior in releases/release-8.1.0.md: Revises release overview and runaway-query descriptions, including wording about avoiding query performance problems and the conditions for automatically lowering query priority or cancelling queries. The comparison table’s described feature behavior is otherwise unchanged.
• observed — Modified behavior in releases/release-8.1.0.md: Corrects the wording of the statement about using expressions as default values when adding a column.
• observed — Modified behavior in releases/release-8.1.0.md: Corrects the description of the tidb_enable_dist_task default setting; it remains ON and enables DXF by default.
• observed — Modified behavior in releases/release-8.1.0.md: Retains the compatibility notes that Lightning distinguishes "false", "", "skip-verify", and "preferred"; TiDB removes shutdown-time forceRebase for AUTO_ID_CACHE=1 tables, with possible nonconsecutive IDs during failover; and TiCDC splits MySQL-sink updates only when their transaction commitTS is less than thresholdTS. Corrects wording in these notes and changes the system-variable table’s change-type header.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the Japanese translation fixes and the three affected release-note versions.
Description check	✅ Passed	The description explains the translation defects, affected files and versions, related issues, AI involvement, and out-of-scope items. It provides sufficient context for review.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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