feat(lex_parser): rename functions and update header guard prefix

- Change header guard from `__SMCC_LEX_PARSER_H__` to `__SCC_LEX_PARSER_H__`
- Prefix all lexer functions with `scc_` (e.g., `lex_parse_char` → `scc_lex_parse_char`)
- Add new helper function `scc_lex_parse_is_identifier_header`
- Update references in source and test files to use new function names
- Replace `core_stream_eof` with `scc_stream_eof` for consistency

libs/lex_parser/tests/test_skip_line.c

@@ -9,13 +9,13 @@ void check_skip_line(const char *str, const char *expect_remaining) {
     scc_probe_stream_t *stream =
         scc_mem_probe_stream_init(&mem_stream, str, scc_strlen(str), false);
 
-    lex_parse_skip_line(stream, &pos);
+    scc_lex_parse_skip_line(stream, &pos);
 
     // Check remaining content
     char buffer[256] = {0};
     int i = 0;
     int ch;
-    while ((ch = scc_probe_stream_consume(stream)) != core_stream_eof &&
+    while ((ch = scc_probe_stream_consume(stream)) != scc_stream_eof &&
            i < 255) {
         buffer[i++] = (char)ch;
     }