add sub-bar usage widget extension with opencode-go support

pi/files/agent/extensions/sub-bar/src/storage.ts

@@ -0,0 +1,61 @@
+/**
+ * Storage abstraction for settings persistence.
+ */
+
+import * as fs from "node:fs";
+import * as path from "node:path";
+
+export interface StorageAdapter {
+	readFile(path: string): string | undefined;
+	writeFile(path: string, contents: string): void;
+	writeFileExclusive(path: string, contents: string): boolean;
+	exists(path: string): boolean;
+	removeFile(path: string): void;
+	ensureDir(path: string): void;
+}
+
+export function createFsStorage(): StorageAdapter {
+	return {
+		readFile(filePath: string): string | undefined {
+			try {
+				return fs.readFileSync(filePath, "utf-8");
+			} catch {
+				return undefined;
+			}
+		},
+		writeFile(filePath: string, contents: string): void {
+			fs.writeFileSync(filePath, contents, "utf-8");
+		},
+		writeFileExclusive(filePath: string, contents: string): boolean {
+			try {
+				fs.writeFileSync(filePath, contents, { flag: "wx" });
+				return true;
+			} catch {
+				return false;
+			}
+		},
+		exists(filePath: string): boolean {
+			return fs.existsSync(filePath);
+		},
+		removeFile(filePath: string): void {
+			try {
+				fs.unlinkSync(filePath);
+			} catch {
+				// Ignore remove errors
+			}
+		},
+		ensureDir(dirPath: string): void {
+			fs.mkdirSync(path.resolve(dirPath), { recursive: true });
+		},
+	};
+}
+
+let activeStorage: StorageAdapter = createFsStorage();
+
+export function getStorage(): StorageAdapter {
+	return activeStorage;
+}
+
+export function setStorage(storage: StorageAdapter): void {
+	activeStorage = storage;
+}