[fix][evaluation] keep experiment status Terminated after retrying items post-termination

[shemingxin66]

背景

实验被终止后，用户手动重试特定 item 时，后端状态机出现两个不符合预期的表现（会话 task-746aac4bd6235c89a69534a7dec0b9a0）：

1. 重试个别 item 时，实验状态机从「终止」变回「进行中」，页面显示的执行中题目数 = 实验并发数 + 1（预期应为 1）。
2. 重试的 item 完成后，实验被塌成「成功/失败」，只显示成功/失败数，不再展示执行中/待执行/终止——即便实验里仍有终止的 item（预期应仍显示「终止」，并分别声明成功/失败/执行中/待执行/终止各计数）。

根因与修复

bug#1（数量脏值）：CompleteExpt 里 stats 的计算与写入（CalculateStats + UpdateByExptID）原本发生在 in-flight item 被标记为 Terminal（terminateIncompleteItemRunLogs / terminateItemTurns）之前，导致 stats 表残留虚高的 processing_cnt（≈终止瞬间的并发数）、少算 terminated_cnt。
修复：删除提前的 UpdateByExptID；在终止收口之后，按 item 主表现值重算 CalculateStats 再落 stats 表。仅在真正终止了行时（statsDirty）才重算，正常完成 / Failed 路径复用首次快照、不多做一次全量扫描。

bug#2（收敛判据）：终态推导判据（原 design D5）刻意排除 TerminatedItemCnt，导致仍含终止 item 的实验被误判为 Success/Failed。
修复：收敛判据新增最高优先级分支——只要 TerminatedItemCnt > 0 一律收敛为 Terminated，前端仍分别展示 成功/失败/执行中/待执行/终止 各计数（DTO 已透传五类）。

影响面

• 仅改动 modules/evaluation/domain/service/expt_manage_execution_impl.go 一个实现文件 + 2 个测试文件，74 增 30 删。
• 无 IDL 变更。
• legacy 与 enforce 两条计数路径都经 CompleteExpt，一处修复即同时覆盖。

验证

• go build ./modules/evaluation/... ✅
• go vet ✅ / gofmt ✅
• go test ./modules/evaluation/domain/service/ 全包通过（260s ok）✅
• 重写了原 D5 单测以反映新语义；新增对 bug#1「重算后写入」不变量的断言。

🤖 Generated with Claude Code

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[codecov]

Codecov Report

❌ Patch coverage is 76.47059% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ation/domain/service/expt_manage_execution_impl.go	76.47%	2 Missing and 2 partials ⚠️

❌ Your patch check has failed because the patch coverage (76.47%) is below the target coverage (80.00%). You can increase the patch coverage or adjust the target coverage.

@@           Coverage Diff           @@
##             main     #670   +/-   ##
=======================================
  Coverage        ?   78.83%           
=======================================
  Files           ?      707           
  Lines           ?    87902           
  Branches        ?        0           
=======================================
  Hits            ?    69298           
  Misses          ?    14611           
  Partials        ?     3993           

Flag	Coverage Δ
unittests	78.83% <76.47%> (?)

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Files with missing lines	Coverage Δ
...ation/domain/service/expt_manage_execution_impl.go	82.49% <76.47%> (ø)

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