Assert the result of the conversion tests

[jdno]

Thirteen tests bound their result to a discarded variable and asserted nothing:

#[test]
fn from_str_returns_name() {
    let _name: TestName = "test".into();
}

That proves the conversion compiles and nothing else. A conversion that returned the wrong value passed, and the name promised a result the test never checked. AGENTS.md also asks that each test hold exactly one assertion, and these held none.

Each test now asserts the value it produces:

#[test]
fn from_str_returns_name() {
    let name: TestName = "test".into();

    assert_eq!("test", name.get());
}

Notes for review

• Affects From<&str>, From<String>, From<i64>, TryFrom<&str> and TryFrom<String> across all seven test files.
• Verified the assertions actually fire, by changing an expected value and confirming the tests fail. They did not fail before this change.
• The duplicate conversion in tests/secret.rs, where from_string_returns_secret converts from a &str, is left alone here and fixed separately.

just pre-commit passes.