Run Fallow quality pass before grant

[horn111]

Description

Pre-grant Fallow quality pass for arc-nano-kit.

This PR fixes the actionable Fallow findings without changing the shipped Arc Receipts behavior:

• exports SDK types that were already part of public signatures
• removes the unused direct viem dependency from the demo app
• deduplicates proof API JSON/error handling
• splits proof polling and watcher internals into smaller helpers
• keeps raw Fallow reports out of the repo

Known remaining item: fallow audit still flags apps/demo/src/app/page.tsx complexity. This is intentionally deferred because it is a broad demo UI refactor, not a grant-blocking correctness issue.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactoring (no functional changes)

Related Issues

N/A

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• SDK typecheck passes
• SDK build passes
• SDK tests pass: 60 tests
• Demo TypeScript check passes
• Demo Next.js build passes
• git diff --check passes
• Fallow dead-code/deps/private-type-leaks/dupes are clean

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Project	Deployment	Actions	Updated (UTC)
arc-nano-kit-demo	Ready	Preview, Comment	Jul 3, 2026 11:33am