fix: refresh pi dependency compatibility

Update Pi packages to 0.79.9 and align pi-ask with current TUI/RPC behavior.

- guard custom ask/settings flows to TUI mode with a clear non-TUI fallback

- reset config cache on extension reload so edited settings are picked up

- clean up remote ask flow listeners on session shutdown

- forward editor focus/invalidation and keep @ file autocomplete explicit

- document the non-TUI contract and cover the compatibility fixes with tests

tests/autocomplete.test.ts

@@ -0,0 +1,9 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { createAskAutocompleteProvider } from "../src/ui/autocomplete.ts";
+
+test("ask autocomplete explicitly triggers on file mention marker", () => {
+	const provider = createAskAutocompleteProvider(process.cwd());
+
+	assert.deepEqual(provider.triggerCharacters, ["@"]);
+});