Align CLI with latest GraphQL availability terminology

[jsmestad]

Summary

• migrate GraphQL usage from deprecated schedule to availability in status/watch/availability flows
• rename CLI command from hd schedule to hd availability and align user-facing labels
• add hd windows command backed by reachabilityWindows query
• include newer verdict fields (policy, policyStatus) and remove invalid afk from createContract input
• add a lightweight GraphQL contract test to ensure command queries reference availability

Testing

• cargo fmt --all
• cargo test

Notes

• this intentionally breaks the old JSON contract (schedule key) and follows backend naming directly (availability) for pre-customer iteration.