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

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

@@ -0,0 +1,71 @@
+/**
+ * Error utilities for the sub-bar extension
+ */
+
+import type { UsageError, UsageErrorCode } from "./types.js";
+
+export function createError(code: UsageErrorCode, message: string, httpStatus?: number): UsageError {
+	return { code, message, httpStatus };
+}
+
+export function noCredentials(): UsageError {
+	return createError("NO_CREDENTIALS", "No credentials found");
+}
+
+export function noCli(cliName: string): UsageError {
+	return createError("NO_CLI", `${cliName} CLI not found`);
+}
+
+export function notLoggedIn(): UsageError {
+	return createError("NOT_LOGGED_IN", "Not logged in");
+}
+
+export function fetchFailed(reason?: string): UsageError {
+	return createError("FETCH_FAILED", reason ?? "Fetch failed");
+}
+
+export function httpError(status: number): UsageError {
+	return createError("HTTP_ERROR", `HTTP ${status}`, status);
+}
+
+export function apiError(message: string): UsageError {
+	return createError("API_ERROR", message);
+}
+
+export function timeout(): UsageError {
+	return createError("TIMEOUT", "Request timed out");
+}
+
+/**
+ * Check if an error should be considered "no data available" vs actual error
+ * These are expected states when provider isn't configured
+ */
+export function isExpectedMissingData(error: UsageError): boolean {
+	const ignoreCodes = new Set<UsageErrorCode>(["NO_CREDENTIALS", "NO_CLI", "NOT_LOGGED_IN"]);
+	return ignoreCodes.has(error.code);
+}
+
+/**
+ * Format error for display in the usage widget
+ */
+export function formatErrorForDisplay(error: UsageError): string {
+	switch (error.code) {
+		case "NO_CREDENTIALS":
+			return "No creds";
+		case "NO_CLI":
+			return "No CLI";
+		case "NOT_LOGGED_IN":
+			return "Not logged in";
+		case "HTTP_ERROR":
+			if (error.httpStatus === 401) {
+				return "token no longer valid – please /login again";
+			}
+			return `${error.httpStatus}`;
+		case "FETCH_FAILED":
+		case "API_ERROR":
+		case "TIMEOUT":
+		case "UNKNOWN":
+		default:
+			return "Fetch failed";
+	}
+}