v0.1.25.59 — authoritative reservation TTL

Authoritative reservation TTL

• Emit remaining_ttl_ms on reservation create and extend responses.
• Recompute the field on idempotent replays; finalized reservations report zero.
• Keep the timing hint outside signed evidence payloads.
• Stabilize replay assertions for the documented dynamic-field carve-out.
• Align generated and runtime schemas on a non-negative TTL.