Several point-feature tests use bare except: pass, so a broken detector passes silently

Found 2026-08-03 while adding regression tests for BRISK/AKAZE (see the opencv5 migration issue, #44). tests/test_image_point_features.py's test_sift, test_surf, test_orb, test_corners, and test_feature_properties all wrap the actual detector call in a bare try: ... except: pass. This means a completely broken detector (e.g. the exact AttributeError: BRISK_create not found bug fixed in #44) would make these tests pass silently instead of failing -- confirmed by construction while writing test_brisk/test_akaze without that pattern: reverting the BRISK/AKAZE fix makes the new tests fail loudly (as expected), but the same revert applied to SIFT/ORB would not be caught by the existing tests at all.

Fix

Remove the bare except: pass from these five tests; assert the real expected outcome directly (matching the pattern used for the new test_brisk/test_akaze). If a specific environment genuinely can't run one of these (e.g. SURF requiring a non-free build flag), skip explicitly with self.skipTest(reason) rather than swallowing all exceptions.

Start in tests/test_image_point_features.py with test_sift, test_surf, test_orb, test_corners, and test_feature_properties, then compare them with test_brisk and test_akaze. Run the point-feature tests and make detector failures surface; where an environment genuinely cannot run a detector, verify that it is skipped explicitly with a reason rather than silently passing.