chore: release 0.6.4

[vvillait88]

Summary

Releases 0.6.4, carrying everything merged since 0.6.3:

• help text for options the API ignores now says they are deprecated, including --refresh (docs: deprecate request options the API ignores #129)
• quota reset documented as a UTC date rather than a timestamp (docs: X-Quota-Reset is a UTC date, not a timestamp #128)

Also in this PR: @agent-score/sdk floor raised to 2.8.1, released today.

Worked with: Varun.

Out of scope: no command behavior changes.

Type of change

• Bug fix (no breaking change)
• New feature (no breaking change)
• Breaking change (existing callers must update)
• Docs, tests, or internal maintenance only

Public API

none.

Test plan

bun run lint, typecheck, test (578 passed, 2 skipped) and build pass locally on this branch.

Checklist

• Tests cover the new behavior, and the suite passes locally
• Lint, format, and type checks pass
• Docs and README examples updated if the public surface changed
• No secrets, credentials, or personal data in the diff or the tests