ci: Test Core 按包两路分片,verify-CLI 拆为独立并行 job

CI 提速:PR 关键路径从 ~13 分钟降到 ~7 分钟。

- Test Core 改为 2 路矩阵,按包分片:scripts/partition-test-shards.mjs 以
  测试文件数为权重做确定性 LPT 均衡(当前全量 573/572)。不用 dogfood 的
  vitest --shard 透传,因为 vitest 4 对测试文件数少于分片数的包直接报错,
  加 --passWithNoTests 后该包在所有分片上都不执行(静默丢覆盖);今天有
  3 个单测试文件的包。required check 名称契约由新增的 test-gate 聚合 job
  以裸 "Test Core" 上下文承载(#3622 教训,同 dogfood-gate)。
- `objectstack verify` CLI 步骤从 dogfood shard 1 尾部(串行 +4.5 分钟)
  拆为并行的 dogfood-verify job,结果并入既有 Dogfood Regression Gate,
  分支保护无需变更。
- temporal-conformance 的 Turbo 缓存回退键从 turbo-test-* 改指
  turbo-build-core-*:test 命名空间分片化后,单个分片不再是其构建闭包
  的超集,而 Build Core 构建全部包。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01U8Ms7unkKxTrmNCX2r1dfs

Author: claude

.changeset/ci-shard-test-core.md

@@ -0,0 +1,8 @@
+---
+---
+
+CI-only: shard the Test Core job by package (deterministic, test-file-count-balanced
+halves via `scripts/partition-test-shards.mjs`), move the dogfood verify-CLI pass into
+its own parallel job aggregated by the existing Dogfood Regression Gate, and repoint
+the temporal-conformance Turbo cache fallback at the Build Core namespace. Releases
+nothing.