refactor(windows): simplify metadata reads and test setup

[jlongster]

Summary

• Read cached Windows terminal metadata in List instead of synchronously asking each actor for a foreground-process refresh that is unsupported on Windows. Unix refresh behavior is unchanged.
• Cover the Windows cached-metadata path with a small actor-independent regression.
• Reuse the daemon test's existing creation helper for customized CreateTerminal requests, removing duplicate request/response plumbing without changing coverage.

This is the final small review-cleanup layer above #18. The full Windows stack received independent reuse, quality/semantics, efficiency, and Windows/FFI ownership reviews. No unsafe/FFI changes, protocol changes, new dependencies, or runtime architecture changes are included here.

Validation

• Local formatting, locked Clippy, full Linux tests and both Miri ownership models are checked before push.
• Native x64/ARM64 and Core CI run on this PR.
• The same uncommitted eight-case focused transport/attachment regression payload will run against this final head after ordinary CI; probe source stays outside Git.

Stack base: windows-subscriptions (#18). No PRs or branches have been merged, and user-owned #10 is untouched.

[jlongster]

Final stack verification

Final tip: 716984d0dac2a6f2646093dbdf7d26b8f1a9deb4 (windows-cleanup, #19).

• Ordinary Windows CI: x64 and ARM64 both passed 64 tests plus 39 standalone library checks, including OS/PE architecture assertions. ARM64 passed after one unchanged build-timeout retry.
• Core CI: Linux 65, macOS 60, and the actual Ghostty-effects/retained-pointer fixtures under both Miri models (6+6) passed.
• Focused regression run: x64 passed all eight unchanged cases, including late-exit attachment completion and controller Drop with a retained receiver clone, actor responsiveness before global shutdown, and joined child cleanup. Framing, ownership, pipe churn, ACL/reparse and startup cases also passed.

Remaining verification gap: the extra focused ARM64 job 100805714049 timed out in native compilation before executing any tests or probes. It is not counted as a pass or a product-test failure. The ordinary ARM64 suite on this exact final head is green. Further optional retries were stopped to keep the finish focused rather than investigate another compiler stall.

Independent reuse, quality/semantics, efficiency and Windows/FFI reviews are complete. No actionable safety or broader design findings remained; the two small cleanup recommendations were applied in #19.

Useful regressions are committed. Larger probe sources remain outside Git. The pre-existing Linux blocked-master-write limitation remains out of scope; no Unix I/O redesign, dependency fork, full Windows CLI port or OpenCode integration was added. Protocol 7 and ownership/handoff rules are unchanged, and user-owned #10 remains separate.

All PRs remain unmerged. Ready-for-review status does not claim the extra ARM64 probe run completed.