fix: replace bool comparison with negation to satisfy clippy

[drzow]

assert!(expr == false) triggers clippy::bool_comparison; use assert!(!expr) instead.

Summary

Fixes #939

Changes

Changed == false to !

Testing

• cargo clippy --workspace --all-targets -- -D warnings passes - not in isolation, needs fix for Fail to compile: cannot create non-exhaustive struct using struct expression #926 first
• cargo test --workspace passes -- as above
• [n/a] Live integration tested (if applicable)

Security

• No new unsafe code
• No secrets or API keys in diff
• User input validated at boundaries