feat(config): add per-auth disable_cooling override support

- Introduced `disable_cooling` metadata field for fine-grained control over cooldown scheduling.
- Updated `Auth` object to include `Metadata` with conditional logic for handling empty states.
- Added YAML configuration support for `disable_cooling` in API key definitions across providers.
- Enhanced unit tests to validate `disable_cooling` behavior in various scenarios.

sdk/cliproxy/auth/types.go

@@ -355,19 +355,28 @@ func (a *Auth) ProxyInfo() string {
 	return "via proxy"
 }
 
-// DisableCoolingOverride returns the auth-file scoped disable_cooling override when present.
+// DisableCoolingOverride returns the auth scoped disable_cooling override when present.
 // The value is read from metadata key "disable_cooling" (or legacy "disable-cooling").
+//
+// NOTE: This override is intentionally "true-only". When the metadata value is false, it is treated
+// as "not set" so the global disable-cooling flag can still take effect.
 func (a *Auth) DisableCoolingOverride() (bool, bool) {
 	if a == nil || a.Metadata == nil {
 		return false, false
 	}
 	if val, ok := a.Metadata["disable_cooling"]; ok {
 		if parsed, okParse := parseBoolAny(val); okParse {
+			if !parsed {
+				return false, false
+			}
 			return parsed, true
 		}
 	}
 	if val, ok := a.Metadata["disable-cooling"]; ok {
 		if parsed, okParse := parseBoolAny(val); okParse {
+			if !parsed {
+				return false, false
+			}
 			return parsed, true
 		}
 	}