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/examples/extensions/subagent/agents.ts

@@ -1,126 +0,0 @@
-/**
- * Agent discovery and configuration
- */
-
-import * as fs from "node:fs";
-import * as path from "node:path";
-import { getAgentDir, parseFrontmatter } from "@mariozechner/pi-coding-agent";
-
-export type AgentScope = "user" | "project" | "both";
-
-export interface AgentConfig {
-	name: string;
-	description: string;
-	tools?: string[];
-	model?: string;
-	systemPrompt: string;
-	source: "user" | "project";
-	filePath: string;
-}
-
-export interface AgentDiscoveryResult {
-	agents: AgentConfig[];
-	projectAgentsDir: string | null;
-}
-
-function loadAgentsFromDir(dir: string, source: "user" | "project"): AgentConfig[] {
-	const agents: AgentConfig[] = [];
-
-	if (!fs.existsSync(dir)) {
-		return agents;
-	}
-
-	let entries: fs.Dirent[];
-	try {
-		entries = fs.readdirSync(dir, { withFileTypes: true });
-	} catch {
-		return agents;
-	}
-
-	for (const entry of entries) {
-		if (!entry.name.endsWith(".md")) continue;
-		if (!entry.isFile() && !entry.isSymbolicLink()) continue;
-
-		const filePath = path.join(dir, entry.name);
-		let content: string;
-		try {
-			content = fs.readFileSync(filePath, "utf-8");
-		} catch {
-			continue;
-		}
-
-		const { frontmatter, body } = parseFrontmatter<Record<string, string>>(content);
-
-		if (!frontmatter.name || !frontmatter.description) {
-			continue;
-		}
-
-		const tools = frontmatter.tools
-			?.split(",")
-			.map((t: string) => t.trim())
-			.filter(Boolean);
-
-		agents.push({
-			name: frontmatter.name,
-			description: frontmatter.description,
-			tools: tools && tools.length > 0 ? tools : undefined,
-			model: frontmatter.model,
-			systemPrompt: body,
-			source,
-			filePath,
-		});
-	}
-
-	return agents;
-}
-
-function isDirectory(p: string): boolean {
-	try {
-		return fs.statSync(p).isDirectory();
-	} catch {
-		return false;
-	}
-}
-
-function findNearestProjectAgentsDir(cwd: string): string | null {
-	let currentDir = cwd;
-	while (true) {
-		const candidate = path.join(currentDir, ".pi", "agents");
-		if (isDirectory(candidate)) return candidate;
-
-		const parentDir = path.dirname(currentDir);
-		if (parentDir === currentDir) return null;
-		currentDir = parentDir;
-	}
-}
-
-export function discoverAgents(cwd: string, scope: AgentScope): AgentDiscoveryResult {
-	const userDir = path.join(getAgentDir(), "agents");
-	const projectAgentsDir = findNearestProjectAgentsDir(cwd);
-
-	const userAgents = scope === "project" ? [] : loadAgentsFromDir(userDir, "user");
-	const projectAgents = scope === "user" || !projectAgentsDir ? [] : loadAgentsFromDir(projectAgentsDir, "project");
-
-	const agentMap = new Map<string, AgentConfig>();
-
-	if (scope === "both") {
-		for (const agent of userAgents) agentMap.set(agent.name, agent);
-		for (const agent of projectAgents) agentMap.set(agent.name, agent);
-	} else if (scope === "user") {
-		for (const agent of userAgents) agentMap.set(agent.name, agent);
-	} else {
-		for (const agent of projectAgents) agentMap.set(agent.name, agent);
-	}
-
-	return { agents: Array.from(agentMap.values()), projectAgentsDir };
-}
-
-export function formatAgentList(agents: AgentConfig[], maxItems: number): { text: string; remaining: number } {
-	if (agents.length === 0) return { text: "none", remaining: 0 };
-	const listed = agents.slice(0, maxItems);
-	const remaining = agents.length - listed.length;
-	return {
-		text: listed.map((a) => `${a.name} (${a.source}): ${a.description}`).join("; "),
-		remaining,
-	};
-}