Fix:update agent variable name rule (#11124)

### What problem does this PR solve?

change:

1. update agent variable name rule.
2. reset() in Canvas doesn't reset the env var.
3. correct log input binding in message component
### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

docker/entrypoint.sh

@@ -187,7 +187,7 @@ function start_mcp_server() {
 }
 
 function ensure_docling() {
-    [[ "${USE_DOCLING}" == "true" ]] || return 0
+    [[ "${USE_DOCLING}" == "true" ]] || { echo "[docling] disabled by USE_DOCLING"; return 0; }
     python3 -c 'import pip' >/dev/null 2>&1 || python3 -m ensurepip --upgrade || true
     DOCLING_PIN="${DOCLING_VERSION:-==2.58.0}"
     python3 -c "import importlib.util,sys; sys.exit(0 if importlib.util.find_spec('docling') else 1)" \