docs: hand off private Windows runtime integration

docs/协作/evidence/windows-runtimes-01/backend.txt

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+PASS defaults and complete bundle activate all tools
+PASS private tools precede original system paths, including spaces
+PASS disabled global preference preserves original environment exactly
+PASS per-tool disabled does not inject its paths
+PASS missing and incomplete bundle never reports active
+PASS Linux and macOS preserve original environment
+PASS case-insensitive PATH becomes one canonical key and survives MCP SDK merge
+PASS overlay introduces no credentials or unrelated variables
+PASS writable private caches and prefixes are scoped to active tools
+PASS overlay idempotence
+PASS IPC patch validation rejects malformed and unknown values
+PASS serialized updates merge toggles and preserve unrelated config
+PASS settings survive module restart without exposing config credentials
+PASS failed atomic save leaves the committed enable policy unchanged
+PASS corrupt, incomplete, and unreadable stored policy never silently enables tools
+Private runtimes: 15 regression groups passed; no Windows executables run.