add El SDK CI/CD pipeline and install script

- .gitea/workflows/sdk-release.yaml: build elc from bootstrap, run tests,
  publish latest release, dispatch el-sdk-updated to downstream repos
- install.sh: one-command El SDK install from Gitea release

el-compiler/runtime/el_runtime.c

@@ -3099,6 +3099,9 @@ el_val_t json_get_raw(el_val_t json_str, el_val_t key) {
     const char* json = EL_CSTR(json_str);
     const char* k    = EL_CSTR(key);
     const char* p = json_find_key(json, k);
+    /* Clear fs_read binary-length hint — result is a fresh null-terminated
+     * string, not the raw file bytes, so Content-Length must use strlen. */
+    _tl_fs_read_len = 0;
     if (!p) return el_wrap_str(el_strdup(""));
     const char* end = json_skip_value(p);
     size_t n = (size_t)(end - p);