v0.1.8

`surge-dispatch` SCUC security loop: lower memory, faster solves, and
adjoint loss sensitivities. Default policy retuned.

Added (`surge-dispatch`)

• Lazy PTDF caching on the SCUC security path — caches build only
  when a contingency actually binds, rather than eagerly per period.
• Adjoint-based DC loss sensitivities replace the explicit per-branch
  Jacobian build in `surge-opf`/`surge-dispatch`, simplifying the
  loss-factor pipeline.

Fixed

• `surge-dispatch`: SCUC security loop now defers early exit by one
  iteration when sys-row loss treatment is active but no solve has
  yet consumed realized loss factors. Previously both
  `ScalarFeedback` and `PenaltyFactors` could silently no-op on
  scenarios with a clean contingency profile.

Performance (`surge-dispatch`)

• Lower SCUC security memory footprint at scale: per-period state is
  released after use rather than retained for the full horizon.
• Faster security wall time via tightened PTDF tolerance, lazy cache
  construction, and adapter-side request reuse.

Changed (defaults)

• `scuc_loss_treatment` defaulted to `penalty_factors` (was
  `scalar_feedback`), paired with the security-loop fix above.
• `scuc_thermal_penalty_multiplier` defaulted to `1.25` (was `10.0`)
  to keep SCUC thermal penalties closer to the configured slack rate.