[v2] Complete in-process lifecycle and platform reliability work

首先阅读 #1934，并确定 #1976、#1983、#1986 和 #2272 已经解决了什么问题。重现剩余的 Windows in-process CI、force-stop、session-disposal 以及 SQLite 关闭行为，然后将 graceful shutdown 与 out-of-process 运行进行对比测量。完成的标准是：具备可靠的 SDK 覆盖、teardown 和资源释放的回归测试、经过论证的不支持组合，以及 maintainer 对所有未实现内容的认可。

Summary

Complete the remaining in-process runtime lifecycle and platform reliability work required for v2.

These are tracked jobs from #1934, not optional investigation topics. First establish what existing work has already completed, then implement the remainder. If new evidence shows an item no longer applies, document it and obtain maintainer confirmation before closing it without implementation.

Original concerns

• Windows in-process CI legs for .NET and Rust were disabled because of a napi-oop cleanup race. The race was thought unlikely to affect real applications, but the CI legs still needed to be re-enabled and teardown shown to be robust after removing napi-oop.
• The underlying runtime did not close SQLite connections after forceStop, and possibly not after session disposal. This left locked files on Windows.
• Graceful SQLite shutdown was suspected of being slow. This was the leading hypothesis in #1934 for in-process CI legs taking approximately 25–50% longer than their out-of-process equivalents.

Required outcomes

• The intended Windows in-process CI coverage is enabled and reliable across SDKs.
• Callback and teardown behavior remains robust after the napi-oop cleanup work.
• Force-stop and session disposal release SQLite connections and do not leave locked files on Windows.
• Graceful shutdown does not have unexplained material performance regressions relative to out-of-process operation.
• Any intentionally unsupported platform or test combination is explicitly justified and documented.

Implementation preparation

• Establish what #1976, #1983, #1986, and #2272 already resolved.
• Reproduce and test any remaining lifecycle or shutdown failures.
• Confirm whether SQLite closure is SDK-owned or requires changes in github/copilot-cli, and link the required runtime work.
• Measure shutdown behavior sufficiently to confirm or reject the SQLite performance hypothesis.
• Escalate for maintainer direction if an external runtime defect cannot reasonably be completed for v2.

Historical context

• #1934
• #1976
• #1983
• #1986
• #2272

Completion

Deliver the required coverage, teardown, resource-release, and shutdown behavior with reliable regression tests. Any item not implemented requires documented contradictory evidence and explicit maintainer agreement.