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/src/modes/interactive/components/earendil-announcement.ts

@@ -1,53 +0,0 @@
-import * as fs from "node:fs";
-import { Container, Image, Spacer, Text } from "@mariozechner/pi-tui";
-import { getBundledInteractiveAssetPath } from "../../../config.js";
-import { theme } from "../theme/theme.js";
-import { DynamicBorder } from "./dynamic-border.js";
-
-const BLOG_URL = "https://mariozechner.at/posts/2026-04-08-ive-sold-out/";
-const IMAGE_FILENAME = "clankolas.png";
-
-let cachedImageBase64: string | undefined;
-let attemptedImageLoad = false;
-
-function loadImageBase64(): string | undefined {
-	if (attemptedImageLoad) {
-		return cachedImageBase64;
-	}
-
-	attemptedImageLoad = true;
-	try {
-		cachedImageBase64 = fs.readFileSync(getBundledInteractiveAssetPath(IMAGE_FILENAME)).toString("base64");
-	} catch {
-		cachedImageBase64 = undefined;
-	}
-	return cachedImageBase64;
-}
-
-export class EarendilAnnouncementComponent extends Container {
-	constructor() {
-		super();
-
-		this.addChild(new DynamicBorder((text) => theme.fg("accent", text)));
-		this.addChild(new Text(theme.bold(theme.fg("accent", "pi has joined Earendil")), 1, 0));
-		this.addChild(new Spacer(1));
-		this.addChild(new Text(theme.fg("muted", "Read the blog post:"), 1, 0));
-		this.addChild(new Text(theme.fg("mdLink", BLOG_URL), 1, 0));
-		this.addChild(new Spacer(1));
-
-		const imageBase64 = loadImageBase64();
-		if (imageBase64) {
-			this.addChild(
-				new Image(
-					imageBase64,
-					"image/png",
-					{ fallbackColor: (text) => theme.fg("muted", text) },
-					{ maxWidthCells: 56, filename: IMAGE_FILENAME },
-				),
-			);
-			this.addChild(new Spacer(1));
-		}
-
-		this.addChild(new DynamicBorder((text) => theme.fg("accent", text)));
-	}
-}