Add comprehensive security tests for masking and shape hardening features

- Introduced red-team expected-fail tests for client masking shape hardening.
- Added integration tests for masking AB envelope blur to improve obfuscation.
- Implemented masking security tests to validate the behavior of masking under various conditions.
- Created tests for masking shape above-cap blur to ensure proper functionality.
- Developed adversarial tests for masking shape hardening to evaluate robustness against attacks.
- Added timing normalization security tests to assess the effectiveness of timing obfuscation.
- Implemented red-team expected-fail tests for timing side-channel vulnerabilities.

src/proxy/client.rs

@@ -1261,3 +1261,15 @@ mod masking_diagnostics_security_tests;
 #[cfg(test)]
 #[path = "tests/client_masking_shape_hardening_security_tests.rs"]
 mod masking_shape_hardening_security_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_shape_hardening_adversarial_tests.rs"]
+mod masking_shape_hardening_adversarial_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_shape_hardening_redteam_expected_fail_tests.rs"]
+mod masking_shape_hardening_redteam_expected_fail_tests;
+
+#[cfg(test)]
+#[path = "tests/client_masking_shape_classifier_fuzz_redteam_expected_fail_tests.rs"]
+mod masking_shape_classifier_fuzz_redteam_expected_fail_tests;