fix: unref advisory monitor handles

[dorukardahan]

Summary

• Unrefs ZeroAPI advisory file watchers and debounce timers.
• Adds a regression test that verifies watcher and timer handles are unrefed.
• Prepares patch release metadata for v3.7.2.

Why

• OpenClaw CLI diagnostics such as openclaw hooks check --json load hook-only plugins to inspect them. ZeroAPI v3.7.1 started advisory watchers during plugin registration, which could keep short-lived CLI diagnostics alive after JSON output was produced.

Tests

• npm test
• JSON parse check
• old version grep, with only historical changelog headings remaining

Non-goals

• No routing policy changes.
• No OpenClaw runtime patch changes in this PR.

[dorukardahan]

@codex review

[chatgpt-codex-connector]

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

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