fix: persist state under plugin-state/ (runner de-privilege)

The managed runner is de-privileged on Windows now (runs as LocalService),
and %ProgramData%\punktfunk is locked read-only to it — so writing config/
cache straight under the config dir fails EPERM. Move the plugin's state to
<config_dir>/plugin-state/playnite, which `punktfunk-host plugins enable`
grants the runner write on. On Linux the runner owns the config dir, so the
path is writable there too. First release, so no migration needed.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/paths.ts

@@ -1,6 +1,6 @@
 // Where the plugin's own files live. The host config-dir resolution mirrors the SDK's `configDir`
 // (`@punktfunk/host` does not re-export it) so we always land in the same place the host and runner
-// use; the plugin owns a `playnite/` subtree under it, created 0700.
+// use; the plugin owns a `plugin-state/playnite/` subtree under it, created 0700.
 import * as fs from "node:fs";
 import * as os from "node:os";
 import * as path from "node:path";
@@ -19,8 +19,18 @@ export const hostConfigDir = (): string => {
 	return path.join(base, "punktfunk");
 };
 
-/** This plugin's private directory: `<config_dir>/playnite`. */
-export const pluginDir = (): string => path.join(hostConfigDir(), "playnite");
+/**
+ * This plugin's private directory: `<config_dir>/plugin-state/playnite`.
+ *
+ * The state lives under `plugin-state/`, not straight under the config dir, because the managed
+ * runner is de-privileged on Windows (`NT AUTHORITY\LocalService`) and the config dir is locked
+ * read-only there — `punktfunk-host plugins enable` grants the runner write on exactly
+ * `plugin-state`. (Mirrors `@punktfunk/host`'s `pluginStateDir`; reimplemented locally like
+ * `hostConfigDir`, since we don't gate on an SDK version bump.) On Linux the runner owns the config
+ * dir, so the same path is writable with no special step.
+ */
+export const pluginDir = (): string =>
+	path.join(hostConfigDir(), "plugin-state", "playnite");
 
 /** `<config_dir>/playnite/config.json` — operator-editable, atomic-written. */
 export const configPath = (): string => path.join(pluginDir(), "config.json");

test/state.test.ts

@@ -0,0 +1,36 @@
+// State persistence lands under `<config_dir>/plugin-state/playnite` — the one dir the
+// de-privileged Windows runner (LocalService) may write. A regression here (writing straight under
+// the config dir) would EPERM under the runner and lose the operator's config.
+import { afterEach, beforeEach, describe, expect, test } from "bun:test";
+import * as fs from "node:fs";
+import * as os from "node:os";
+import * as path from "node:path";
+import { loadConfig, saveRawConfig } from "../src/state.js";
+
+let root: string;
+let saved: string | undefined;
+
+beforeEach(() => {
+	saved = process.env.PUNKTFUNK_CONFIG_DIR;
+	root = fs.mkdtempSync(path.join(os.tmpdir(), "pn-state-"));
+	process.env.PUNKTFUNK_CONFIG_DIR = root;
+});
+afterEach(() => {
+	if (saved === undefined) delete process.env.PUNKTFUNK_CONFIG_DIR;
+	else process.env.PUNKTFUNK_CONFIG_DIR = saved;
+	fs.rmSync(root, { recursive: true, force: true });
+});
+
+describe("state location", () => {
+	test("persists under plugin-state/playnite and round-trips", () => {
+		saveRawConfig({ playniteDir: "/games/playnite" });
+		expect(
+			fs.existsSync(path.join(root, "plugin-state", "playnite", "config.json")),
+		).toBe(true);
+		// Not written straight under the config dir (the LocalService-unwritable location).
+		expect(fs.existsSync(path.join(root, "playnite", "config.json"))).toBe(
+			false,
+		);
+		expect(loadConfig().playniteDir).toBe("/games/playnite");
+	});
+});