refactor(host): migrate IO and SQLite onto scoped lifecycle

[fffonion]

Summary

• migrate async IO onto the scoped resource and operation lifecycle
• add scoped SQLite host functions with bounded workers, cancellation, reset, and reusable connection cleanup
• keep adapter policy and state outside the VM core

Stack

• Base: refactor(vm): split runtime state and add scoped lifecycle #16
• Next: feat(vm): add capability-aware async execution and lifecycle consumption #23
• Commits: 44dac76, 9a525de

Validation

• focused IO and SQLite lifecycle suites
• repeated pending-reset coverage
• cargo test --workspace --all-targets --all-features
• strict workspace Clippy and feature-isolation checks