fix: accept stringified ambient cycle counts

[zerone0x]

Summary

• allow the ambient cycle tool to deserialize numeric counters from either JSON numbers or integer strings
• apply the same lenient handling to next_schedule.wake_in_minutes
• add regression coverage for stringified counts

Fixes #106

Test Plan

• cargo fmt --all
• cargo test -q test_end_cycle_input (blocked locally: missing pkg-config/OpenSSL development metadata; sudo requires a password on this host)

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