Add browser extension and shell completions (Milestones 12-13)

M12: Browser Extension
- Chrome/Edge Manifest V3 extension
- Popup UI for saving pages
- Context menu integration (save page/selection/link)
- Background service worker
- Content script for extraction

M13: Shell Completions
- Bash, Zsh, Fish, PowerShell completions
- Dynamic node ID completion
- Dynamic tag completion
- Dynamic graph completion
- Auto-install command (--install)

src/cli/index.ts

@@ -25,6 +25,7 @@ import { backupCommand, restoreDbCommand, listBackupsCommand } from './commands/
 import { graphsCommand, useCommand, initCommand } from './commands/graphs';
 import { smartSearchCommand, ssCommand, whatCommand, contextAwareCommand } from './commands/smart';
 import { tuiCommand, uiCommand } from './commands/tui';
+import { completionsCommand, getNodesCommand, getTagsCommand, getGraphsCommand } from './commands/completions';
 import { closeDb } from '../core/db';
 import { migrateOldDatabase } from '../core/db';
 
@@ -75,6 +76,10 @@ program.addCommand(whatCommand);
 program.addCommand(contextAwareCommand);
 program.addCommand(tuiCommand);
 program.addCommand(uiCommand);
+program.addCommand(completionsCommand);
+program.addCommand(getNodesCommand);
+program.addCommand(getTagsCommand);
+program.addCommand(getGraphsCommand);
 
 // Check for old database migration
 migrateOldDatabase();