feat(lattice): add durable schedule authority core

[mgazza]

Summary

Adds the pure BatPred-side v0.4 atomic schedule compiler and durable authority state machine.

• compiles a complete PredBat plan into an absolute UTC schedule with at most eight slots
• emits field-10 replacement and digest-guarded cancellation transitions
• validates retained gateway schedule capabilities and gateway-local coordinates before dispatch
• persists command identity, installed authority, terminal receipts, and UNKNOWN quarantine time for restart-safe reconciliation
• distinguishes requested, receiver-applied, and cancelled plan digests
• keeps writer exclusion after valid_until; only a proven replacement or cancellation ending transition can change/release it
• requires matching cancellation digest, release flag, and durable/native readback before cancellation APPLIED releases authority
• reconciles the original command ID without republishing after restart or uncertainty

Safety

This tranche is deliberately disconnected from PredBat.execute_plan, save_plan, and all live transports. It cannot write to a gateway or inverter. Live wiring will be a separate, default-off stacked PR.

The implementation fails closed on:

• UNKNOWN, malformed/conflicting receipts, corrupt state, stale fencing, and storage/transport uncertainty
• bare or mismatched cancellation APPLIED
• wrong provider/access route for an ending transition
• command collisions, no-active-schedule, plan-digest mismatch, and unconfirmed authority release
• lease expiry or schedule valid_until without a proven ending transition

UNKNOWN and its first quarantine timestamp are durably paired; a corrupt or half-present pair suppresses the legacy writer.

Verification

• 47/47 focused schedule-authority tests pass on Python 3.9 and Python 3.14
• Black, Ruff, cspell, pre-commit, and diff checks pass
• GitNexus staged audit: LOW risk, two files, zero affected existing execution flows
• independent review blockers were corrected before publication

Stack

• Base: feat(lattice): dispatch durable charge power intents #4318
• Contract: feat(schedule): complete v0.4 authority contract Predictive-Cloud-Ltd/lattice-spec#38
• Tracking: Predictive-Cloud-Ltd/predbat-saas-infra#557
• Epic: Predictive-Cloud-Ltd/predbat-saas-infra#466