chore: drop non-code junk (pi-mono-reference, runtime state, root duplicates)

Remove files that should never have been tracked:

- pi-mono-reference/: 688-file copy of an upstream monorepo, zero imports,
  used only as offline human reference
- build/electron-builder.runtime.json: environment-specific build artifact
  with hardcoded local paths
- state/cancel-signal-state.json: runtime state written by the app
- prompt.txt, logo.svg (root): exact duplicates of the canonical copies
  under .planning/archive/ and assets/

Add state/ to .gitignore so future runtime state stays out.

pi-mono-reference/packages/ai/test/google-gemini-cli-empty-stream.test.ts

@@ -1,108 +0,0 @@
-import { afterEach, describe, expect, it, vi } from "vitest";
-import { streamGoogleGeminiCli } from "../src/providers/google-gemini-cli.js";
-import type { Context, Model } from "../src/types.js";
-
-const originalFetch = global.fetch;
-
-afterEach(() => {
-	global.fetch = originalFetch;
-	vi.restoreAllMocks();
-});
-
-describe("google-gemini-cli empty stream retry", () => {
-	it("retries empty SSE responses without duplicate start", async () => {
-		const emptyStream = new ReadableStream<Uint8Array>({
-			start(controller) {
-				controller.close();
-			},
-		});
-
-		const sse = `${[
-			`data: ${JSON.stringify({
-				response: {
-					candidates: [
-						{
-							content: { role: "model", parts: [{ text: "Hello" }] },
-							finishReason: "STOP",
-						},
-					],
-					usageMetadata: {
-						promptTokenCount: 1,
-						candidatesTokenCount: 1,
-						totalTokenCount: 2,
-					},
-				},
-			})}`,
-		].join("\n\n")}\n\n`;
-
-		const encoder = new TextEncoder();
-		const dataStream = new ReadableStream<Uint8Array>({
-			start(controller) {
-				controller.enqueue(encoder.encode(sse));
-				controller.close();
-			},
-		});
-
-		let callCount = 0;
-		const fetchMock = vi.fn(async () => {
-			callCount += 1;
-			if (callCount === 1) {
-				return new Response(emptyStream, {
-					status: 200,
-					headers: { "content-type": "text/event-stream" },
-				});
-			}
-			return new Response(dataStream, {
-				status: 200,
-				headers: { "content-type": "text/event-stream" },
-			});
-		});
-
-		global.fetch = fetchMock as typeof fetch;
-
-		const model: Model<"google-gemini-cli"> = {
-			id: "gemini-2.5-flash",
-			name: "Gemini 2.5 Flash",
-			api: "google-gemini-cli",
-			provider: "google-gemini-cli",
-			baseUrl: "https://cloudcode-pa.googleapis.com",
-			reasoning: false,
-			input: ["text"],
-			cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
-			contextWindow: 128000,
-			maxTokens: 8192,
-		};
-
-		const context: Context = {
-			messages: [{ role: "user", content: "Say hello", timestamp: Date.now() }],
-		};
-
-		const stream = streamGoogleGeminiCli(model, context, {
-			apiKey: JSON.stringify({ token: "token", projectId: "project" }),
-		});
-
-		let startCount = 0;
-		let doneCount = 0;
-		let text = "";
-
-		for await (const event of stream) {
-			if (event.type === "start") {
-				startCount += 1;
-			}
-			if (event.type === "done") {
-				doneCount += 1;
-			}
-			if (event.type === "text_delta") {
-				text += event.delta;
-			}
-		}
-
-		const result = await stream.result();
-
-		expect(text).toBe("Hello");
-		expect(result.stopReason).toBe("stop");
-		expect(startCount).toBe(1);
-		expect(doneCount).toBe(1);
-		expect(fetchMock).toHaveBeenCalledTimes(2);
-	});
-});