fix(xref/headings): trim inputs, add version/series fallback in getHeading

Per Copilot review:
- Trim spec and id before lookup (validation checked trim but passed raw)
- Add version-stripped and series-shortname fallback in getHeading so
  both "cssom-view-1" and "cssom-view" resolve headings correctly
- Also resolves specTitle via stripped form as fallback

Author: marcoscaceres

routes/xref/headings.post.ts

@@ -47,7 +47,7 @@ export default function route(req: IRequest, res: Response) {
     }
   }
   const result = queries.map(({ spec, id }) => {
-    const heading = store.getHeading(spec, id);
+    const heading = store.getHeading(spec.trim(), id.trim());
     if (!heading) {
       return { spec, id, error: "not found" };
     }

routes/xref/lib/store.ts

@@ -41,17 +41,46 @@ export class Store {
     id: string,
   ): (HeadingEntry & { specTitle: string }) | null {
     const normalizedSpec = spec.toLowerCase();
-    const specHeadings = this.headings[normalizedSpec];
+    let specHeadings = this.headings[normalizedSpec];
+    // Fallback: try stripping version suffix (e.g., cssom-view → cssom-view-1)
+    // or adding it via specmap lookup
+    if (!specHeadings) {
+      const stripped = normalizedSpec.replace(/-\d+$/, "");
+      if (stripped !== normalizedSpec) {
+        specHeadings = this.headings[stripped];
+      }
+      if (!specHeadings) {
+        // Try resolving series shortname to versioned via specmap
+        for (const [specId, entry] of this.specmapEntries()) {
+          if (entry.shortname === normalizedSpec || entry.shortname === stripped) {
+            specHeadings = this.headings[specId];
+            if (specHeadings) break;
+          }
+        }
+      }
+    }
     if (!specHeadings) return null;
 
     const heading = specHeadings[id];
     if (!heading) return null;
 
     return {
       ...heading,
-      specTitle: this.specTitleByShortname.get(normalizedSpec) || spec,
+      specTitle: this.specTitleByShortname.get(normalizedSpec)
+        || this.specTitleByShortname.get(normalizedSpec.replace(/-\d+$/, ""))
+        || spec,
     };
   }
+
+  private *specmapEntries() {
+    for (const group of Object.values(this.specmap)) {
+      for (const [specId, entry] of Object.entries(
+        group as Record<string, { shortname: string; title: string }>
+      )) {
+        yield [specId, entry] as const;
+      }
+    }
+  }
 }
 
 /** Read a required JSON data file. Throws if missing. */