Fix go-to-definition for vars imported via :refer

When a namespace uses :refer to import specific vars (e.g.,
[tui.events :refer [key=]]), clojure-lsp only populates the :to
field on the :refer declaration entry, not on subsequent usages.

This fix:
- Builds a refer-map from entries with :refer true
- Looks up the target namespace for usages missing :to
- Properly links usages like (key= event \q) to their definition

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/scip_clojure/core.clj

@@ -118,13 +118,23 @@
     (.build builder)))
 
 (defn var-usage->occurrence
-  "Convert a clojure-lsp var-usage to SCIP Occurrence (reference)."
-  [{:keys [to name] :as var-usage}]
-  (let [builder (Scip$Occurrence/newBuilder)]
-    (.addAllRange builder (position->range var-usage))
-    (.setSymbol builder (make-symbol to name))
-    ;; No role bits = reference
-    (.build builder)))
+  "Convert a clojure-lsp var-usage to SCIP Occurrence (reference).
+
+   For vars imported via :refer, the :to field may be nil in usage entries.
+   The refer-map provides a lookup from var name to target namespace for these cases.
+
+   Entries with :refer true have :to populated and represent the import declaration.
+   Entries without :refer are actual usages and may need refer-map lookup."
+  ([var-usage]
+   (var-usage->occurrence var-usage {}))
+  ([{:keys [to name] :as var-usage} refer-map]
+   (let [target-ns (or to (get refer-map name))
+         builder (Scip$Occurrence/newBuilder)]
+     (when target-ns  ;; Only create occurrence if we can resolve the target
+       (.addAllRange builder (position->range var-usage))
+       (.setSymbol builder (make-symbol target-ns name))
+       ;; No role bits = reference
+       (.build builder)))))
 
 (defn ns-definition->occurrence
   "Convert a namespace definition to SCIP Occurrence."
@@ -269,6 +279,13 @@
         relative-path (uri->relative-path uri project-root)
         {:keys [var-definitions var-usages namespace-definitions namespace-usages namespace-alias]} file-analysis
 
+        ;; Build refer-map: for vars imported via :refer, map var-name -> target-namespace
+        ;; These entries have :refer true and :to populated
+        refer-map (->> (or var-usages [])
+                       (filter :refer)
+                       (map (fn [{:keys [name to]}] [name to]))
+                       (into {}))
+
         ;; Create occurrences for definitions
         def-occurrences (map var-definition->occurrence (or var-definitions []))
 
@@ -276,7 +293,8 @@
         def-symbols (map var-definition->symbol-info (or var-definitions []))
 
         ;; Create occurrences for usages (references)
-        usage-occurrences (map var-usage->occurrence (or var-usages []))
+        ;; Pass refer-map to resolve referred vars that don't have :to
+        usage-occurrences (keep #(var-usage->occurrence % refer-map) (or var-usages []))
 
         ;; Namespace definitions
         ns-def-occurrences (map ns-definition->occurrence (or namespace-definitions []))