feat: add pi-condense with default enablement

extensions/condense-config.ts

@@ -0,0 +1,33 @@
+import { mkdirSync, readFileSync, renameSync, writeFileSync } from "node:fs";
+import { dirname, join } from "node:path";
+
+export type CondenseDefaultResult = "updated" | "unchanged" | "skipped-invalid";
+
+function isObject(value: unknown): value is Record<string, unknown> {
+	return value !== null && typeof value === "object" && !Array.isArray(value);
+}
+
+/** Enable pi-condense only when the user has not already chosen an enabled state. */
+export function ensureCondenseEnabledDefault(agentDir: string): CondenseDefaultResult {
+	const targetPath = join(agentDir, "settings.json");
+	let settings: Record<string, unknown> = {};
+
+	try {
+		const parsed: unknown = JSON.parse(readFileSync(targetPath, "utf8"));
+		if (!isObject(parsed)) return "skipped-invalid";
+		settings = parsed;
+	} catch (error) {
+		if ((error as NodeJS.ErrnoException).code !== "ENOENT") return "skipped-invalid";
+	}
+
+	const existing = settings.contextPrune;
+	if (existing !== undefined && !isObject(existing)) return "skipped-invalid";
+	if (isObject(existing) && Object.hasOwn(existing, "enabled")) return "unchanged";
+
+	settings.contextPrune = { ...(existing ?? {}), enabled: true };
+	mkdirSync(dirname(targetPath), { recursive: true });
+	const temporaryPath = `${targetPath}.my-pi.tmp`;
+	writeFileSync(temporaryPath, `${JSON.stringify(settings, null, 2)}\n`, "utf8");
+	renameSync(temporaryPath, targetPath);
+	return "updated";
+}