test: add policy boundary condition tests for evaluateAction [FaaFyfxR9WAQrL7FcAgEHJvztd8cVMxvjHRS55rw1nwH]

[waterWang]

Summary

Adds deterministic boundary condition tests for evaluateAction covering all edge cases specified in the issue.

Tests added

• Invalid amounts: NaN, zero, and negative transfer amounts are blocked
• Per-action cap: amounts above cap blocked, exactly at cap allowed
• Daily cap: exactly reaching daily cap allowed, exceeding by smallest practical value blocked
• Intent note: shorter than 12 trimmed characters blocked, exactly 12 chars allowed
• Whitespace handling: leading/trailing whitespace does not bypass recipient allowlist or intent note length check

Also fixed a pre-existing unused import warning in receipt.test.ts.

Closes #3

[FeeeeelixWong]

Closing this PR because it is not an independent, focused submission. PRs #7, #8, and #9 currently point to the same head commit (b506729) and contain both the Issue #3 policy tests and the Issue #2 receipt verifier. This duplicates the two active pull requests and mixes unrelated task scopes.