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/config.ts

@@ -0,0 +1,131 @@
+import { existsSync, readFileSync } from "fs";
+import { homedir } from "os";
+import { dirname, join, resolve } from "path";
+import { fileURLToPath } from "url";
+
+// =============================================================================
+// Package Detection
+// =============================================================================
+
+const __filename = fileURLToPath(import.meta.url);
+const __dirname = dirname(__filename);
+
+/**
+ * Detect if we're running as a Bun compiled binary.
+ * Bun binaries have import.meta.url containing "$bunfs" (Bun's virtual filesystem path)
+ */
+export const isBunBinary = import.meta.url.includes("$bunfs");
+
+// =============================================================================
+// Package Asset Paths (shipped with executable)
+// =============================================================================
+
+/**
+ * Get the base directory for resolving package assets (themes, package.json, README.md, CHANGELOG.md).
+ * - For Bun binary: returns the directory containing the executable
+ * - For Node.js (dist/): returns __dirname (the dist/ directory)
+ * - For tsx (src/): returns parent directory (the package root)
+ */
+export function getPackageDir(): string {
+	if (isBunBinary) {
+		// Bun binary: process.execPath points to the compiled executable
+		return dirname(process.execPath);
+	}
+	// Node.js: check if package.json exists in __dirname (dist/) or parent (src/ case)
+	if (existsSync(join(__dirname, "package.json"))) {
+		return __dirname;
+	}
+	// Running from src/ via tsx - go up one level to package root
+	return dirname(__dirname);
+}
+
+/**
+ * Get path to built-in themes directory (shipped with package)
+ * - For Bun binary: theme/ next to executable
+ * - For Node.js (dist/): dist/theme/
+ * - For tsx (src/): src/theme/
+ */
+export function getThemesDir(): string {
+	if (isBunBinary) {
+		return join(dirname(process.execPath), "theme");
+	}
+	// __dirname is either dist/ or src/ - theme is always a subdirectory
+	return join(__dirname, "theme");
+}
+
+/** Get path to package.json */
+export function getPackageJsonPath(): string {
+	return join(getPackageDir(), "package.json");
+}
+
+/** Get path to README.md */
+export function getReadmePath(): string {
+	return resolve(join(getPackageDir(), "README.md"));
+}
+
+/** Get path to CHANGELOG.md */
+export function getChangelogPath(): string {
+	return resolve(join(getPackageDir(), "CHANGELOG.md"));
+}
+
+// =============================================================================
+// App Config (from package.json piConfig)
+// =============================================================================
+
+const pkg = JSON.parse(readFileSync(getPackageJsonPath(), "utf-8"));
+
+export const APP_NAME: string = pkg.piConfig?.name || "pi";
+export const CONFIG_DIR_NAME: string = pkg.piConfig?.configDir || ".pi";
+export const VERSION: string = pkg.version;
+
+// e.g., PI_CODING_AGENT_DIR or TAU_CODING_AGENT_DIR
+export const ENV_AGENT_DIR = `${APP_NAME.toUpperCase()}_CODING_AGENT_DIR`;
+
+// =============================================================================
+// User Config Paths (~/.pi/agent/*)
+// =============================================================================
+
+/** Get the agent config directory (e.g., ~/.pi/agent/) */
+export function getAgentDir(): string {
+	return process.env[ENV_AGENT_DIR] || join(homedir(), CONFIG_DIR_NAME, "agent");
+}
+
+/** Get path to user's custom themes directory */
+export function getCustomThemesDir(): string {
+	return join(getAgentDir(), "themes");
+}
+
+/** Get path to models.json */
+export function getModelsPath(): string {
+	return join(getAgentDir(), "models.json");
+}
+
+/** Get path to oauth.json */
+export function getOAuthPath(): string {
+	return join(getAgentDir(), "oauth.json");
+}
+
+/** Get path to settings.json */
+export function getSettingsPath(): string {
+	return join(getAgentDir(), "settings.json");
+}
+
+/** Get path to tools directory */
+export function getToolsDir(): string {
+	return join(getAgentDir(), "tools");
+}
+
+/** Get path to slash commands directory */
+export function getCommandsDir(): string {
+	return join(getAgentDir(), "commands");
+}
+
+/** Get path to sessions directory */
+export function getSessionsDir(): string {
+	return join(getAgentDir(), "sessions");
+}
+
+/** Get path to debug log file */
+export function getDebugLogPath(): string {
+	return join(getAgentDir(), `${APP_NAME}-debug.log`);
+}