chore: add Aislop quality gate

[codesoda]

Summary

• add the generated Aislop config, rules, and GitHub Actions quality gate
• improve the project score through targeted cleanup and safer test fixtures
• use scoped Aislop ignore directives for intentional synthetic URL/token fixtures

Validation

• aislop scan: 97/100
• aislop ci --human: passed
• cargo test: passed
• cargo clippy --all-targets --all-features -- -D warnings: passed
• cargo fmt --all -- --check: passed
• cargo doc --no-deps --document-private-items: passed

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