fix(api): report a removed subpath as a breaking change instead of aborting

The generated check still imported a subpath that is no longer built, so tsc
failed on the import line, which maps to no assertion, and the script exited
with code 2 ("could not run") without listing the removed files. The subpath is
already reported as removed, so it no longer gets type assertions.

Author: hyanmandian

scripts/api.ts

@@ -586,6 +586,8 @@ const renderBreakingCheck = ({
 		const current = headSubpaths.entries.get(subpath);
 		const kept = compareSubpath({ subpath, text, current, baseSubpaths, headSubpaths, removed });
 
+		if (current === undefined) continue;
+
 		addModule(`subpath "${subpath}"`, `_${identifier(subpath)}`, subpath, kept);
 	}