Add native cycle-and-soak with minimum soak time and interleaving

[JB09]

Closes #234.

Summary

Adds a native cycle-and-soak mode to sequences via a new cycle: config block. Each zone’s total runtime is split into evenly distributed cycles capped at a configurable maximum, with a guaranteed minimum soak between a zone’s own cycles. During a zone’s soak, other pending zones in the same sequence run (interleaving), so the soak window is used productively instead of sitting idle — matching how commercial controllers (RainMachine, Rain Bird) handle slow-infiltrating soils like clay.

Backwards compatible: sequences without a cycle: block behave exactly as before.

Config

sequences:
  - name: "Front/Side"
    cycle:
      max_duration: "00:45"   # cap per cycle (runoff threshold)
      min_duration: "00:10"   # floor; never run a cycle shorter than this
      min_soak: "01:00"       # guaranteed soak between a zone's own cycles
    zones:
      - zone_id: 1
        duration: "02:15"     # total; split into cycles automatically
      # ...

Behavior

• Even-distribution split — num_cycles = ceil(total / max_duration), then per_cycle = total / num_cycles. Avoids a tiny trailing cycle (e.g. 45 min → 3 × 15, never 15 + 15 + 15 + remainder).
• Minimum cycle floor — num_cycles is capped at floor(total / min_duration) so no cycle runs shorter than min_duration. If a zone’s total is below min_duration, it runs once.
• Guaranteed minimum soak — between a zone’s consecutive cycles, at least min_soak is enforced.
• Interleaving (most-time-remaining-first) — during a zone’s soak, the scheduler runs the pending zone with the most time remaining, keeping one-zone-at-a-time within the sequence. This fills soak windows productively and minimizes total run time.
• Drop-out — zones with fewer cycles finish early and are skipped in later passes.
• adjust_time integration — when a zone’s total is set via adjust_time, the cycle logic re-derives the split from the new total, so integrations that push a daily total per zone (e.g. Smart Irrigation) work without the caller dividing by a cycle count. This also sidesteps the repeat multiplication behavior reported in Smart Irrigation integration with Irrigation Unlimited not fully functional #203 / Despite different configuration the watering time is limited to one hour ("magically") #211.

Testing

• Unit tests covering split math, the min_duration floor, min_soak enforcement, interleaving order (most-time-remaining-first), drop-out, and adjust_time re-derivation.
• Validated end-to-end on a live Home Assistant instance (6 zones across 2 concurrent sequences). The run order was reconstructed from entity state history. With Front = 3 cycles, Side Left = 2, Side Right = 1, the observed order confirmed interleaving and selection logic:
  • Front c1 → (soak) → Side Left c1 — Side Left chosen over Side Right because it had more time remaining (2 min vs 1 min), confirming most-time-remaining-first rather than zone-label order.
  • Subsequent cycles continued interleaving, with each zone dropping out as it completed and min_soak respected between a given zone’s cycles.

Other findings

• cancel during a cycled run — I noticed cancel does not always terminate all remaining cycles of an in-progress cycled run (a reload cleared it).