chore(release): 0.6.4

[willytop8]

Release 0.6.4.

Bumps package.json/package-lock.json to 0.6.4 and promotes the Unreleased CHANGELOG section to ## 0.6.4. No source changes beyond the version/changelog — the shipped code is the auto-continue hardening already merged via #31.

Changelog

• Re-check session status and recent messages after an auto-continue cooldown, pause immediately for human intervention, Plan-agent switches, permission rejection, aborts, and provider errors, and abort an accepted continuation when the user takes control.
• Persist one continuation claim per goal execution epoch and source assistant turn to prevent sequential duplicate idle events, while preserving the initiating agent, model, and variant on every continuation prompt.

Local npm run release:check passes (exit 0).