checks: `missing-nonce` / `missing-event-for-admin-change` / `unprotected-*` unit tests never assert `function_name` or `line`

[unrealtim-tech]

Labels: bug, checks-crate
Crate: checks

Description
Several checks' unit tests assert only findings.len() and never the finding's function_name or line, so a regression in which method is flagged (or where the finding is anchored — see the method.span() vs fn_token.span() issue) passes silently:

• crates/checks/src/missing_nonce.rs — flags_missing_nonce / ignores_with_nonce
• crates/checks/src/missing_event_for_admin_change.rs — flags_missing_event
• crates/checks/src/unprotected_token_mint.rs — flags_unprotected_mint
• crates/checks/src/unprotected_contract_deployment.rs — flags_unprotected_deployer
• crates/checks/src/large_loop.rs — flags_loop / flags_while

By contrast auth.rs, admin.rs, transfer.rs assert hits[0].function_name / severity.

Acceptance Criteria

• Add assert_eq!(hits[0].function_name, "<expected>") (and a line assertion where the fixture makes it meaningful) to the listed tests.

Difficulty: beginner