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/coding-agent/test/footer-width.test.ts

@@ -1,115 +0,0 @@
-import { visibleWidth } from "@mariozechner/pi-tui";
-import { beforeAll, describe, expect, it } from "vitest";
-import type { AgentSession } from "../src/core/agent-session.js";
-import type { ReadonlyFooterDataProvider } from "../src/core/footer-data-provider.js";
-import { FooterComponent } from "../src/modes/interactive/components/footer.js";
-import { initTheme } from "../src/modes/interactive/theme/theme.js";
-
-type AssistantUsage = {
-	input: number;
-	output: number;
-	cacheRead: number;
-	cacheWrite: number;
-	cost: { total: number };
-};
-
-function createSession(options: {
-	sessionName: string;
-	modelId?: string;
-	provider?: string;
-	reasoning?: boolean;
-	thinkingLevel?: string;
-	usage?: AssistantUsage;
-}): AgentSession {
-	const usage = options.usage;
-	const entries =
-		usage === undefined
-			? []
-			: [
-					{
-						type: "message",
-						message: {
-							role: "assistant",
-							usage,
-						},
-					},
-				];
-
-	const session = {
-		state: {
-			model: {
-				id: options.modelId ?? "test-model",
-				provider: options.provider ?? "test",
-				contextWindow: 200_000,
-				reasoning: options.reasoning ?? false,
-			},
-			thinkingLevel: options.thinkingLevel ?? "off",
-		},
-		sessionManager: {
-			getEntries: () => entries,
-			getSessionName: () => options.sessionName,
-			getCwd: () => "/tmp/project",
-		},
-		getContextUsage: () => ({ contextWindow: 200_000, percent: 12.3 }),
-		modelRegistry: {
-			isUsingOAuth: () => false,
-		},
-	};
-
-	return session as unknown as AgentSession;
-}
-
-function createFooterData(providerCount: number): ReadonlyFooterDataProvider {
-	const provider = {
-		getGitBranch: () => "main",
-		getExtensionStatuses: () => new Map<string, string>(),
-		getAvailableProviderCount: () => providerCount,
-		onBranchChange: (callback: () => void) => {
-			void callback;
-			return () => {};
-		},
-	};
-
-	return provider;
-}
-
-describe("FooterComponent width handling", () => {
-	beforeAll(() => {
-		initTheme(undefined, false);
-	});
-
-	it("keeps all lines within width for wide session names", () => {
-		const width = 93;
-		const session = createSession({ sessionName: "한글".repeat(30) });
-		const footer = new FooterComponent(session, createFooterData(1));
-
-		const lines = footer.render(width);
-		for (const line of lines) {
-			expect(visibleWidth(line)).toBeLessThanOrEqual(width);
-		}
-	});
-
-	it("keeps stats line within width for wide model and provider names", () => {
-		const width = 60;
-		const session = createSession({
-			sessionName: "",
-			modelId: "模".repeat(30),
-			provider: "공급자",
-			reasoning: true,
-			thinkingLevel: "high",
-			usage: {
-				input: 12_345,
-				output: 6_789,
-				cacheRead: 0,
-				cacheWrite: 0,
-				cost: { total: 1.234 },
-			},
-		});
-		const footer = new FooterComponent(session, createFooterData(2));
-
-		const lines = footer.render(width);
-		for (const line of lines) {
-			expect(visibleWidth(line)).toBeLessThanOrEqual(width);
-		}
-	});
-});