fix: ignore string literal contents in emit text scans

[ivov]

Negation of a comparison no longer flips an operator that appears inside a string literal:

!("x == y" == s)

Previously, the inner == was flipped to != instead of the outer comparison, producing the wrong condition.

Also, match over a non-literal subject no longer fails to compile when an arm body contains a string literal whose contents happen to spell the synthesized subject temp:

match make_p() {
  _ => "subject_1",
}

Previously, the _ = subject_1 discard was suppressed, leaving the temp declared and unused.

[github-actions]

Released in lisette-v0.2.1