Add Arc Testnet proof mode

[horn111]

Description

Adds Arc Testnet Proof Mode for Arc Receipts.

This update lets a receipt prove its connection to a real Arc Testnet transaction without asking the demo to send transactions or store private keys. Builders can paste a Memo-wrapped USDC tx hash, verify it against the generated memo payment request, and get block/log proof plus an Arcscan link.

Flow covered:

• create invoice
• build memo payment request
• verify Arc Testnet tx receipt
• match Memo event
• match USDC Transfer
• attach onchain proof to receipt
• keep signed webhook inbox + replay flow working

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Refactoring

Related Issues

Closes #

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have added tests that prove my fix/feature works
• New and existing tests pass locally with my changes
• I have updated the documentation accordingly
• I have updated the CHANGELOG.md

Testing

• npm.cmd run typecheck
• node_modules\.bin\tsc.cmd --noEmit --project apps/demo/tsconfig.json --incremental false
• npm.cmd run test --workspaces --if-present -- --reporter=dot
• git diff --check
• npm.cmd run build in apps/demo
• Local browser check on http://localhost:3005

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Project	Deployment	Actions	Updated (UTC)
arc-nano-kit-demo	Ready	Preview, Comment	Jul 1, 2026 5:38pm