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/web-ui/src/tools/index.ts

@@ -1,46 +0,0 @@
-import type { ToolResultMessage } from "@mariozechner/pi-ai";
-import "./javascript-repl.js"; // Auto-registers the renderer
-import "./extract-document.js"; // Auto-registers the renderer
-import { getToolRenderer, registerToolRenderer } from "./renderer-registry.js";
-import { BashRenderer } from "./renderers/BashRenderer.js";
-import { DefaultRenderer } from "./renderers/DefaultRenderer.js";
-import type { ToolRenderResult } from "./types.js";
-
-// Register all built-in tool renderers
-registerToolRenderer("bash", new BashRenderer());
-
-const defaultRenderer = new DefaultRenderer();
-
-// Global flag to force default JSON rendering for all tools
-let showJsonMode = false;
-
-/**
- * Enable or disable show JSON mode
- * When enabled, all tool renderers will use the default JSON renderer
- */
-export function setShowJsonMode(enabled: boolean): void {
-	showJsonMode = enabled;
-}
-
-/**
- * Render tool - unified function that handles params, result, and streaming state
- */
-export function renderTool(
-	toolName: string,
-	params: any | undefined,
-	result: ToolResultMessage | undefined,
-	isStreaming?: boolean,
-): ToolRenderResult {
-	// If showJsonMode is enabled, always use the default renderer
-	if (showJsonMode) {
-		return defaultRenderer.render(params, result, isStreaming);
-	}
-
-	const renderer = getToolRenderer(toolName);
-	if (renderer) {
-		return renderer.render(params, result, isStreaming);
-	}
-	return defaultRenderer.render(params, result, isStreaming);
-}
-
-export { getToolRenderer, registerToolRenderer };