feat(request-help): add BSK_REQUEST_HELP=off to disable blocking help requests (#53)

* feat(request-help): add BSK_REQUEST_HELP=off to disable blocking help requests

* style(extension): format HelpOutcome union per biome

* docs(skill): condense BSK_REQUEST_HELP section

crates/bsk-protocol/src/tools/human_loop.rs

@@ -95,6 +95,9 @@ pub enum HelpOutcome {
     /// The page navigated while waiting (full reload or SPA URL change).
     /// Deprecated: navigation alone should not end a help request.
     Navigated,
+    /// request-help is disabled by configuration (`BSK_REQUEST_HELP=off`):
+    /// the call returns immediately without ever showing the overlay.
+    Disabled,
 }
 
 impl HelpOutcome {
@@ -105,6 +108,7 @@ impl HelpOutcome {
             Self::TimedOut => "timed_out",
             Self::Completed => "completed",
             Self::Navigated => "navigated",
+            Self::Disabled => "disabled",
         }
     }
 }
@@ -202,6 +206,10 @@ mod tests {
             serde_json::to_value(HelpOutcome::Navigated).unwrap(),
             json!("navigated")
         );
+        assert_eq!(
+            serde_json::to_value(HelpOutcome::Disabled).unwrap(),
+            json!("disabled")
+        );
     }
 
     #[test]