perf(extension): parallelize async operations and cache checks

src/opencodeService.ts

@@ -6,6 +6,8 @@ export interface GenerateOptions {
     model?: string;
 }
 
+let opencodeAvailableCache: boolean | null = null;
+
 const DEFAULT_PROMPT = `You are a helpful assistant that generates git commit messages.
 Generate a concise Conventional Commit message (max 72 characters for the subject line).
 Format: <type>(<scope>): <description>
@@ -15,9 +17,13 @@ Types: feat, fix, refactor, docs, style, test, chore, perf, ci, build, revert
 Only output the commit message, nothing else.`;
 
 export async function isOpenCodeAvailable(): Promise<boolean> {
+    if (opencodeAvailableCache !== null) {
+        return opencodeAvailableCache;
+    }
     return new Promise((resolve) => {
         exec("which opencode", (error: ExecException | null) => {
-            resolve(!error);
+            opencodeAvailableCache = !error;
+            resolve(opencodeAvailableCache);
         });
     });
 }
@@ -32,8 +38,10 @@ export async function generateCommitMessage(
         );
     }
 
-    const diff = await getGitDiff();
-    const repoRoot = await getRepositoryRoot();
+    const [diff, repoRoot] = await Promise.all([
+        getGitDiff(),
+        getRepositoryRoot(),
+    ]);
 
     const config = vscode.workspace.getConfiguration("aiCommitExt");
     const model = options.model || config.get<string>("model", "");