feat(coding-agent): configurable app name and config dir for forks (#95)

- Add piConfig to package.json for app name and config directory
- Consolidate paths.ts into config.ts with clearer naming
- Fix Bun binary detection (changed from %7EBUN to $bunfs)
- Update all hardcoded paths to use config.ts exports
- getThemesDir() for built-in themes, getCustomThemesDir() for user themes

packages/coding-agent/src/tools-manager.ts

@@ -1,12 +1,13 @@
 import chalk from "chalk";
 import { spawnSync } from "child_process";
 import { chmodSync, createWriteStream, existsSync, mkdirSync, renameSync, rmSync } from "fs";
-import { arch, homedir, platform } from "os";
+import { arch, platform } from "os";
 import { join } from "path";
 import { Readable } from "stream";
 import { finished } from "stream/promises";
+import { getToolsDir } from "./config.js";
 
-const TOOLS_DIR = join(homedir(), ".pi", "agent", "tools");
+const TOOLS_DIR = getToolsDir();
 
 interface ToolConfig {
 	name: string;