fix(signal-tracker): firefox and chromium loop over different stack traces (@Leonabcd123) (monkeytypegame#7754)

### Description

First signal's first frame in `frames` array in
https://github.com/monkeytypegame/monkeytype/blob/82bf09564c2fdaaeb8273c638ec1eb7e7e6eb3cb/frontend/src/ts/dev/signal-tracker.ts#L35

Chromium:

`at getCallerInfo
(http://localhost:3000/ts/dev/signal-tracker.ts?t=1774961577350:5:16)`

Firefox:


`DEV.hooks.afterRegisterGraph@http://localhost:3000/ts/dev/signal-tracker.ts?t=1774961577350:84:34`

They both should be referring to `getCallerInfo`, but only chromium
does, because firefox slices off that frame in the code linked above,
while chromium slices off the string "Error".

Doesn't really matter because the `getCallerInfo` frame will be skipped
anyways, but this should still be done to make behavior more consistent
across different browsers.

Author: Leonabcd123

frontend/src/ts/dev/signal-tracker.ts

@@ -32,14 +32,14 @@ type SolidOwner = {
 function getCallerInfo(): { isUserCode: boolean; source: string } {
   const stack = new Error().stack;
   if (stack === undefined) return { isUserCode: false, source: "" };
-  const frames = stack.split("\n").slice(1);
+  const frames = stack.split("\n");
 
   if (frames.some((f) => f.includes("useRefWithUtils"))) {
     return { isUserCode: false, source: "" };
   }
 
   for (const frame of frames.toReversed()) {
-    if (frame === "") continue;
+    if (frame === "" || frame === "Error") continue;
     if (frame.includes("signal-tracker")) continue;
     if (frame.includes("solid-js")) continue;
     if (frame.includes("@solid-refresh")) continue;

frontend/src/ts/test/test-ui.ts

@@ -227,7 +227,7 @@ async function joinOverlappingHints(
   activeWordLetters: ElementsWithUtils,
   hintElements: HTMLCollection,
 ): Promise<void> {
-  const [isWordRightToLeft, _isFullMatch] = Strings.isWordRightToLeft(
+  const [isWordRightToLeft] = Strings.isWordRightToLeft(
     TestWords.words.getCurrent(),
     TestState.isLanguageRightToLeft,
     TestState.isDirectionReversed,