perf: reuse Windows rollout rewrite worker

[Dailin521]

Summary

• reuse one persistent PowerShell worker for Windows Node rollout rewrites
• preserve per-target transaction journal ordering and crash recovery
• stop rewriting the complete backup manifest after every rollout on all Node platforms
• keep legacy backup restore compatibility and non-Windows rewrite behavior unchanged

Verification

• npm test: 207/207 passed
• Windows worker protocol and special-path integration tests passed
• crash windows before acknowledgement and before journal applied are covered
• 100-file local benchmark used one worker and completed in about 1.1 seconds

[Dailin521]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: 70d57fb329

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