[codex] fix incorrect-modifier revert detection

[timeless-hayoka]

What changed

• Fixed incorrect-modifier so it recognizes revert("...") modifiers by matching the real revert(string) signature.
• Extended the revert detection to cover custom-error reverts, which Slither models as revert <custom error signature>.
• Added a regression fixture for Solidity 0.8.4 covering both string reverts and custom-error reverts.

Why

incorrect-modifier was flagging modifiers that already revert on the false path, because the detector matched revert(string instead of the actual revert(string) signature. Custom-error reverts were also missed.

Validation

• uv run pytest tests/e2e/detectors/test_detectors.py -k modifier_reverts --insta update
• uv run pytest tests/e2e/detectors/test_detectors.py -k ModifierDefaultDetection

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