feat: add exec pathPrepend config

src/config/schema.ts

@@ -146,6 +146,7 @@ const FIELD_LABELS: Record<string, string> = {
   "tools.exec.security": "Exec Security",
   "tools.exec.ask": "Exec Ask",
   "tools.exec.node": "Exec Node Binding",
+  "tools.exec.pathPrepend": "Exec PATH Prepend",
   "tools.message.allowCrossContextSend": "Allow Cross-Context Messaging",
   "tools.message.crossContext.allowWithinProvider": "Allow Cross-Context (Same Provider)",
   "tools.message.crossContext.allowAcrossProviders": "Allow Cross-Context (Across Providers)",
@@ -323,6 +324,8 @@ const FIELD_HELP: Record<string, string> = {
     'Optional allowlist of model ids (e.g. "gpt-5.2" or "openai/gpt-5.2").',
   "tools.exec.notifyOnExit":
     "When true (default), backgrounded exec sessions enqueue a system event and request a heartbeat on exit.",
+  "tools.exec.pathPrepend":
+    "Directories to prepend to PATH for exec runs (gateway/sandbox).",
   "tools.message.allowCrossContextSend":
     "Legacy override: allow cross-context sends across all providers.",
   "tools.message.crossContext.allowWithinProvider":