fix: retain completed results during live editing

src/components/ExplanationTree.tsx

@@ -8,6 +8,7 @@ export interface ExplanationTreeProps {
   readonly root?: NormalizedRegexNode;
   readonly selectedId?: string;
   readonly flags?: readonly string[];
+  readonly stale?: boolean;
   readonly onSelect: (node: NormalizedRegexNode) => void;
 }
 
@@ -165,6 +166,7 @@ export function ExplanationTree({
   root,
   selectedId,
   flags = [],
+  stale = false,
   onSelect,
 }: ExplanationTreeProps) {
   const totalNodes = useMemo(() => (root ? countNodes(root) : 0), [root]);
@@ -191,8 +193,18 @@ export function ExplanationTree({
           <p className="eyebrow">Pattern structure</p>
           <h2 id="explanation-heading">Explanation tree</h2>
         </div>
-        <span className="provenance-badge">
-          Deterministic · syntax provider
+        <span
+          className={`provenance-badge ${stale ? "is-stale" : ""}`}
+          data-testid={stale ? "stale-pattern-syntax" : undefined}
+          title={
+            stale
+              ? "This is the last parsed pattern. Its ranges are not applied to the current editor."
+              : undefined
+          }
+        >
+          {stale
+            ? "Stale snapshot · checking current pattern"
+            : "Deterministic · syntax provider"}
         </span>
       </header>
       {totalNodes > renderedNodes ? (