docs: simplify quickstart examples and make them bare-friendly

Created by: gatteo

Cleans up the Node/Bare quickstart and account management snippets:

• Drop the try/catch wrappers that were just noise in the example flow (kept them in the dedicated error-handling guides and where they actually demonstrate a guard).
• Use wdk.dispose() to close wallet connections instead of process.exit(), since process isn't available in Bare by default. The complete quickstart now runs and exits cleanly under both node app.js and bare app.js.