Add metadataEqualIgnoringTimestamps() function to compare metadata JSON
without timestamp/expired/expires_in/last_refresh/access_token fields.
This prevents unnecessary file writes when only these fields change
during refresh, breaking the fsnotify event → Watcher callback → refresh loop.
Key insight: Google OAuth returns a new access_token on each refresh,
which was causing file writes and triggering the refresh loop.
Fixes antigravity channel excessive log generation issue.
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Co-Authored-By: Claude <noreply@anthropic.com>
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