feat: add sync, update, and remove commands

- sync: scans plugins and updates registry.json
- update: checks and updates plugins to match registry
- remove: removes installed plugin with --yes and --remove-deps options
- registry.json stored at project root with plugin metadata and _sourcePath

src/commands/sync.js

@@ -0,0 +1,75 @@
+import fs from 'fs-extra';
+import path from 'path';
+import chalk from 'chalk';
+
+const PLUGINS_DIR = path.resolve('src/plugins');
+const REGISTRY_PATH = path.resolve('registry.json');
+
+/**
+ * Sync registry.json with installed plugins.
+ * Scans all plugins in src/plugins/ and updates registry.json
+ */
+export async function syncCommand() {
+  console.log(chalk.blue('Syncing registry...'));
+
+  // Load existing registry or create new one
+  let registry = { lastUpdated: new Date().toISOString(), plugins: {} };
+
+  if (await fs.pathExists(REGISTRY_PATH)) {
+    try {
+      registry = await fs.readJson(REGISTRY_PATH);
+    } catch (err) {
+      console.warn(chalk.yellow('⚠️  Could not read existing registry, creating new one'));
+    }
+  }
+
+  // Scan plugins directory
+  if (!await fs.pathExists(PLUGINS_DIR)) {
+    console.warn(chalk.yellow('⚠️  No plugins directory found'));
+    await fs.writeJson(REGISTRY_PATH, registry, { spaces: 2 });
+    console.log(chalk.green(`✅ Registry updated at ${path.relative(process.cwd(), REGISTRY_PATH)}`));
+    return;
+  }
+
+  const entries = await fs.readdir(PLUGINS_DIR, { withFileTypes: true });
+  let updated = 0;
+  let added = 0;
+
+  for (const entry of entries) {
+    if (!entry.isDirectory()) continue;
+
+    const manifestPath = path.join(PLUGINS_DIR, entry.name, 'manyplug.json');
+    if (!await fs.pathExists(manifestPath)) continue;
+
+    try {
+      const manifest = await fs.readJson(manifestPath);
+      const pluginName = manifest.name || entry.name;
+
+      // Check if plugin exists in registry and version changed
+      const existing = registry.plugins[pluginName];
+      if (!existing) {
+        added++;
+      } else if (existing.version !== manifest.version) {
+        updated++;
+      }
+
+      registry.plugins[pluginName] = {
+        ...manifest,
+        _syncedAt: new Date().toISOString(),
+        _sourcePath: path.join('src/plugins', entry.name)
+      };
+    } catch (err) {
+      console.warn(chalk.yellow(`⚠️  Failed to read ${entry.name}: ${err.message}`));
+    }
+  }
+
+  // Update timestamp
+  registry.lastUpdated = new Date().toISOString();
+
+  await fs.writeJson(REGISTRY_PATH, registry, { spaces: 2 });
+
+  console.log(chalk.green(`✅ Registry synced`));
+  console.log(chalk.gray(`   Added: ${added}`));
+  console.log(chalk.gray(`   Updated: ${updated}`));
+  console.log(chalk.gray(`   Total plugins: ${Object.keys(registry.plugins).length}`));
+}