Parallelize ExCk return-type lookups in prewarm, hoist beam setup out of loop

Previously prewarmStructFieldsFromText made sequential ReturnTypeStruct
calls (2s timeout each) in a loop, also calling getBeamProcess+Ready
for every iteration. On files with many var=Mod.func() patterns, these
sequential calls could hold the BEAM process for extended periods while
a completion-triggered ReturnTypeStruct call waited behind them.

Changes:
- Fire all ExCk ReturnTypeStruct calls in parallel goroutines so they
  complete as fast as the BEAM can process them, minimizing the window
  where the prewarm contends with completion requests.
- Hoist getBeamProcess + Ready out of the loop — same BEAM process
  for all calls, no need to look it up and check readiness per call.
- All ExCk calls share a single 2s context timeout instead of each
  getting its own, preventing runaway goroutines.

Author: JesseHerrick

internal/lsp/server.go

@@ -1515,7 +1515,7 @@ func (s *Server) prewarmStructFieldsFromText(_ string, filePath, text string) {
 	tf := NewTokenizedFile(text)
 
 	seen := make(map[string]bool)
-	warmed := 0
+	var warmed int
 
 	// Pre-warm from struct literal references (%Module{}).
 	refs := tf.StructModuleRefs()
@@ -1535,39 +1535,46 @@ func (s *Server) prewarmStructFieldsFromText(_ string, filePath, text string) {
 	// Pre-warm from function call return types via ExCk.
 	// Scan the entire file for var = Module.func(...) patterns.
 	calls := tf.AllVariableFunctionCalls()
-	for _, call := range calls {
-		aliases := tf.ExtractAliasesInScope(call.Line)
-		s.mergeAliasesFromUseTokenized(tf, aliases)
-		resolvedModule := tf.ResolveModuleExpr(call.Module, call.Line)
-		fullCallModule := s.resolveModuleWithNesting(resolvedModule, aliases, filePath, call.Line)
-		if fullCallModule == "" {
-			continue
-		}
-
+	if len(calls) > 0 {
 		buildRoot := s.structFieldBuildRoot(filePath)
-		if buildRoot == "" {
-			continue
-		}
-
-		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
-		bp := s.getBeamProcess(ctx, buildRoot)
-		if bp == nil {
-			cancel()
-			continue
-		}
-		if err := bp.Ready(ctx); err != nil {
+		if buildRoot != "" {
+			ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+			bp := s.getBeamProcess(ctx, buildRoot)
+			if bp != nil && bp.Ready(ctx) == nil {
+				type excResult struct {
+					structModule string
+				}
+				results := make([]excResult, len(calls))
+				var wg sync.WaitGroup
+				for i, call := range calls {
+					aliases := tf.ExtractAliasesInScope(call.Line)
+					s.mergeAliasesFromUseTokenized(tf, aliases)
+					resolvedModule := tf.ResolveModuleExpr(call.Module, call.Line)
+					fullCallModule := s.resolveModuleWithNesting(resolvedModule, aliases, filePath, call.Line)
+					if fullCallModule == "" {
+						continue
+					}
+					wg.Add(1)
+					go func(idx int, mod, fn string, arity int) {
+						defer wg.Done()
+						structModule, err := bp.ReturnTypeStruct(ctx, mod, fn, arity)
+						if err == nil && structModule != "" {
+							results[idx] = excResult{structModule: structModule}
+						}
+					}(i, fullCallModule, call.Function, call.Arity)
+				}
+				wg.Wait()
+				for _, res := range results {
+					if res.structModule == "" || seen[res.structModule] {
+						continue
+					}
+					seen[res.structModule] = true
+					s.prewarmStructFields(filePath, res.structModule)
+					warmed++
+				}
+			}
 			cancel()
-			continue
-		}
-
-		structModule, err := bp.ReturnTypeStruct(ctx, fullCallModule, call.Function, call.Arity)
-		cancel()
-		if err != nil || structModule == "" || seen[structModule] {
-			continue
 		}
-		seen[structModule] = true
-		s.prewarmStructFields(filePath, structModule)
-		warmed++
 	}
 
 	if s.debug && warmed > 0 {