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/lexer/tests/test_run.c

@@ -70,11 +70,11 @@ int main(int argc, char *argv[]) {
     scc_cstring_clear(&stream->name);
     scc_cstring_append_cstr(&stream->name, file_name, strlen(file_name));
     scc_lexer_init(&lexer, stream);
-    lexer_tok_t tok;
+    scc_lexer_tok_t tok;
 
     while (1) {
         scc_lexer_get_valid_token(&lexer, &tok);
-        if (tok.type ==  SCC_TOK_EOF) {
+        if (tok.type == SCC_TOK_EOF) {
             break;
         }
         LOG_DEBUG("token `%s` at %s:%u:%u", scc_get_tok_name(tok.type),