base: fail loudly when extract_locales.js runs outside the repo root

[dajiaohuang]

Fixes #2122.

source_paths and locale_path in base/tools/extract_locales.js are relative to the current working directory, and a missing source path is skipped with continue. Run from anywhere but the repository root, every path is skipped: nothing is extracted, nothing is reported, and the script still exits 0. Since locale_path is relative as well, the output directory normally does not exist at that location, so no file is written either - the command looks like it succeeded.

let found = false;

for (let path of source_paths) {
	if (!fs_exists(path)) {
		continue;
	}
	found = true;
	...
}

if (!found) {
	console.log("No source paths found - run this script from the repository root.");
	std.exit(1);
}

fs_writefile(locale_path, JSON.stringify(out, Object.keys(out).sort(), 4));

This mirrors the existing "Locale code not set!" guard at the top of the same file.

Verification

Scratch tree: paint/sources/demo.c with two tr("...") strings, paint/sources/nodes_material/n.c with one, and an existing paint/assets/locale/zz.json holding a real translation plus a stale key. Driven with the committed base/tools/bin/windows_x64/amake.exe.

Run from paint/:

	stdout	exit	zz.json
before	(none)	0	not written
after	No source paths found - run this script from the repository root.	1	not written

Run from the repository root - the supported path:

	stdout	exit	generated locale
before	(none)	0	3 keys, existing translation preserved
after	(none)	0	byte-identical to before

So the correct-cwd behaviour is unchanged; only the silent failure now reports itself. std.exit(1) is used rather than the bare std.exit() at line 11 so the failure is detectable from a script.

Single file, guard only - no extraction or output-format change.

🤖 Generated with Claude Code