Fix ESP32-S31-WROOM-3 symbol failing to load in KiCad

The easyeda2kicad.py-generated file had an unquoted URL as the
(generator ...) value: '(generator https://github.com/uPesy/...)'.
Bare/unquoted s-expression tokens can't contain ':' or '/', which broke
KiCad's parser and made the whole library silently fail to load (the
symbol was present on disk and correctly registered in fp/sym-lib-table,
but invisible in KiCad). Wrapped the value in quotes.

Also added a check_library.py rule to catch this class of error (an
unquoted generator value containing ':' or '/') automatically going
forward.

scripts/check_library.py

@@ -119,6 +119,14 @@ def check_symbols(report: Report) -> list[tuple[str, Path]]:
         if not parens_balanced(text):
             report.error(f"[SYM] {path.relative_to(ROOT)}: unbalanced parentheses")
 
+        gen_m = re.search(r'\(generator\s+([^\s")]+)', text)
+        if gen_m and re.search(r'[:/]', gen_m.group(1)):
+            report.error(
+                f"[SYM] {path.relative_to(ROOT)}: unquoted '(generator {gen_m.group(1)})' "
+                f"contains ':' or '/' -- this breaks KiCad's parser and silently makes the "
+                f"whole library fail to load; wrap the value in double quotes"
+            )
+
         digest = lc.sha256_file(path)
         if digest in seen_hash:
             report.warn(