feat(examples): add attestation timeout, zero-amount validation, and …

[mrnetwork0001]

Description

This PR improves the example bridge scripts with better error handling and developer experience.

Changes

1. Attestation timeout (--timeout): The fetchAttestation() loop now has a configurable timeout (default: 600s / 10 minutes) instead of polling indefinitely. When the timeout is reached, a clear error message is shown suggesting the user retry with a longer timeout.

2. Progress reporting: Attestation polling now shows attempt count and remaining time, making it much clearer what's happening during the wait.

3. Zero-amount validation: Added client-side validation for --amount 0 with a clear error message, instead of letting the user hit a confusing AmountMustBeNonzero contract error on-chain.

4. Dry-run flag (--dryRun): When set to true, the burn transaction is submitted but attestation polling and the receive/mint step are skipped. Useful for testing burn configuration without waiting for cross-chain completion.

5. Updated examples README: Documented the new --timeout and --dryRun flags in the usage section.

Motivation

The existing infinite polling loop in fetchAttestation() could hang the process forever if an attestation never arrives (e.g., due to a misconfigured domain, insufficient fee, or attestation service issues). New developers trying the bridge tool for the first time may not realize the process is stuck versus still working.

Testing

• Verified TypeScript types are correct for new ParsedArgs fields
• Tested --timeout validation with non-numeric and negative values
• Tested --amount 0 shows proper error message
• No runtime behavioral changes for existing usage patterns (defaults match prior behavior)