feat: add npx CLI entry point with install, runtime, and IDE detection commands

Replaces the old git-clone installer with a direct npm package copy workflow.
Supports 13 IDE auto-detection targets, runtime delegation to Bun worker,
and pure Node.js install path (no Bun required for installation).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/npx-cli/utils/paths.ts

@@ -0,0 +1,152 @@
+/**
+ * Shared path utilities for the NPX CLI.
+ *
+ * All platform-specific path logic is centralized here so that every command
+ * resolves directories in exactly the same way, regardless of OS.
+ */
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from 'fs';
+import { homedir } from 'os';
+import { dirname, join } from 'path';
+import { fileURLToPath } from 'url';
+
+// ---------------------------------------------------------------------------
+// Platform detection
+// ---------------------------------------------------------------------------
+
+export const IS_WINDOWS = process.platform === 'win32';
+
+// ---------------------------------------------------------------------------
+// Core paths
+// ---------------------------------------------------------------------------
+
+/** Root of the Claude Code config directory. */
+export function claudeConfigDirectory(): string {
+  return process.env.CLAUDE_CONFIG_DIR || join(homedir(), '.claude');
+}
+
+/** Marketplace install directory for thedotmack. */
+export function marketplaceDirectory(): string {
+  return join(claudeConfigDirectory(), 'plugins', 'marketplaces', 'thedotmack');
+}
+
+/** Top-level plugins directory. */
+export function pluginsDirectory(): string {
+  return join(claudeConfigDirectory(), 'plugins');
+}
+
+/** Path to `known_marketplaces.json`. */
+export function knownMarketplacesPath(): string {
+  return join(pluginsDirectory(), 'known_marketplaces.json');
+}
+
+/** Path to `installed_plugins.json`. */
+export function installedPluginsPath(): string {
+  return join(pluginsDirectory(), 'installed_plugins.json');
+}
+
+/** Path to `~/.claude/settings.json`. */
+export function claudeSettingsPath(): string {
+  return join(claudeConfigDirectory(), 'settings.json');
+}
+
+/** Plugin cache directory for a specific version. */
+export function pluginCacheDirectory(version: string): string {
+  return join(pluginsDirectory(), 'cache', 'thedotmack', 'claude-mem', version);
+}
+
+/** claude-mem data directory (default `~/.claude-mem`). */
+export function claudeMemDataDirectory(): string {
+  return join(homedir(), '.claude-mem');
+}
+
+// ---------------------------------------------------------------------------
+// NPM package root (where the NPX package lives on disk)
+// ---------------------------------------------------------------------------
+
+/**
+ * Resolve the root of the installed npm package.
+ *
+ * The CLI entry point lives at `<pkg>/dist/cli/index.js`. Walking up
+ * from `import.meta.url` (or `__dirname` equivalent) we reach the
+ * package root where `plugin/` can be found.
+ */
+export function npmPackageRootDirectory(): string {
+  const currentFilePath = fileURLToPath(import.meta.url);
+  // <pkg>/dist/npx-cli/utils/paths.js  ->  up 3 levels  ->  <pkg>
+  return join(dirname(currentFilePath), '..', '..', '..');
+}
+
+/**
+ * Path to the `plugin/` directory bundled inside the npm package.
+ */
+export function npmPackagePluginDirectory(): string {
+  return join(npmPackageRootDirectory(), 'plugin');
+}
+
+// ---------------------------------------------------------------------------
+// Version helpers
+// ---------------------------------------------------------------------------
+
+/**
+ * Read the current plugin version from the npm package's
+ * `plugin/.claude-plugin/plugin.json` (preferred) or from `package.json`.
+ */
+export function readPluginVersion(): string {
+  // Try plugin.json first (authoritative for plugin version)
+  const pluginJsonPath = join(npmPackagePluginDirectory(), '.claude-plugin', 'plugin.json');
+  if (existsSync(pluginJsonPath)) {
+    try {
+      const pluginJson = JSON.parse(readFileSync(pluginJsonPath, 'utf-8'));
+      if (pluginJson.version) return pluginJson.version;
+    } catch {
+      // Fall through to package.json
+    }
+  }
+
+  // Fall back to package.json at package root
+  const packageJsonPath = join(npmPackageRootDirectory(), 'package.json');
+  if (existsSync(packageJsonPath)) {
+    try {
+      const packageJson = JSON.parse(readFileSync(packageJsonPath, 'utf-8'));
+      if (packageJson.version) return packageJson.version;
+    } catch {
+      // Unable to read
+    }
+  }
+
+  return '0.0.0';
+}
+
+// ---------------------------------------------------------------------------
+// Installation detection
+// ---------------------------------------------------------------------------
+
+/** Returns true if the plugin appears to be installed in the marketplace dir. */
+export function isPluginInstalled(): boolean {
+  const marketplaceDir = marketplaceDirectory();
+  return existsSync(join(marketplaceDir, 'plugin', '.claude-plugin', 'plugin.json'));
+}
+
+// ---------------------------------------------------------------------------
+// JSON file helpers
+// ---------------------------------------------------------------------------
+
+export function ensureDirectoryExists(directoryPath: string): void {
+  if (!existsSync(directoryPath)) {
+    mkdirSync(directoryPath, { recursive: true });
+  }
+}
+
+export function readJsonFileSafe(filepath: string): any {
+  if (!existsSync(filepath)) return {};
+  try {
+    return JSON.parse(readFileSync(filepath, 'utf-8'));
+  } catch {
+    return {};
+  }
+}
+
+export function writeJsonFileAtomic(filepath: string, data: any): void {
+  ensureDirectoryExists(dirname(filepath));
+  writeFileSync(filepath, JSON.stringify(data, null, 2) + '\n', 'utf-8');
+}