run: critic can raise a run's step ceiling mid-flight (CriticHandle.MaxSteps)

Prerequisite for a full-fidelity mort agentcritic adapter (which adjusts a
healthy-but-long run's iteration budget, not just its deadline). executus's
CriticHandle was deadline+steer only; this adds the dynamic step ceiling above
an unchanged majordomo (which already exposes WithMaxStepsFunc).

- run.RunInfo += MaxIterations (the run's base ceiling, so a critic can raise it
  relative to the baseline).
- run.CriticHandle += MaxSteps() int — polled by the executor each step via
  agent.WithMaxStepsFunc; <=0 defers to the base. The executor uses
  WithMaxStepsFunc(critic.MaxSteps) when a critic is active, else WithMaxSteps.
- critic battery: handle.maxSteps (initialised from RunInfo.MaxIterations) +
  MaxSteps(); Decision gains RaiseStepsBy so an Escalator can raise the ceiling
  alongside ExtendBy. ExtendOnce default is unchanged (time-only).

Test: a critic returning MaxSteps=5 lets a base-MaxIterations=1 run complete two
tool-dispatch steps past the base ceiling. Core stays battery-free (run doesn't
import critic).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

run/ports.go

@@ -48,6 +48,9 @@ type RunInfo struct {
 	ParentRunID string
 	Inputs      map[string]any
 	StartedAt   time.Time
+	// MaxIterations is the run's base tool-dispatch step ceiling, so a critic can
+	// raise it relative to the baseline (see CriticHandle.MaxSteps).
+	MaxIterations int
 }
 
 // RunStats is the terminal roll-up a recorder's Close writes. Mirrors mort's
@@ -129,6 +132,11 @@ type CriticHandle interface {
 	// Deadline returns the current hard-kill deadline (the critic may extend
 	// it); the executor binds the run context to it. Zero = no hard deadline.
 	Deadline() time.Time
+	// MaxSteps returns the current tool-dispatch step ceiling, polled by the
+	// executor each step (via majordomo WithMaxStepsFunc) so a critic can raise a
+	// healthy-but-long run's iteration budget mid-flight. Return <= 0 to defer to
+	// the run's base MaxIterations.
+	MaxSteps() int
 	// Stop ends monitoring when the run finishes.
 	Stop()
 }