Dead-code elimination removes textfieldGetString calls used in conditional branches #11

Bug Description

Perry's codegen eliminates textfieldGetString() calls when the result variable is only used inside a conditional branch (e.g., if (user.length > 0)).

Reproduction

const userRaw = textfieldGetString(userField);
const user = (typeof userRaw === 'string' && userRaw.length > 0) ? userRaw : '';
const passRaw = textfieldGetString(passField);
const pass = (typeof passRaw === 'string' && passRaw.length > 0) ? passRaw : '';

// user and pass are only used inside this if:
if (user.length > 0 && pass.length > 0) {
  uri = 'mongodb://' + encodeURIComponent(user) + ':' + encodeURIComponent(pass) + '@' + host;
}

The textfieldGetString(userField) and textfieldGetString(passField) calls are eliminated entirely (confirmed via Rust debug prints — only 4 of 6 expected calls execute).

The same code pattern works for name/host/port because those variables are used unconditionally in later code.

Expected Behavior

Side-effectful native function calls should never be eliminated, even if the result is only used conditionally.