Expedition autopilot Phase 2: auto-harvest on room entry

Each walked room gets one auto-harvest pass across every applicable
action (forage, scavenge, mine, fish in water zones, plus the class-
restricted essence/commune). Class/kill/event gates are inherited
from the manual harvest path.

Stop rules:
- Rare+ nodes are NOT auto-attempted; they pause the walk via
  stopRareNode so the player spends the attempt deliberately.
- Standard/Elite/Patrol interrupts hard-stop the walk (stopEnded on
  death, new stopHarvestCombat on survive).
- Noise interrupts apply threat+2 and continue, matching manual
  !harvest behavior.

Display:
- Per-room compact footer ("+2 Scrap Iron, +1 Shadow Herb · 1 fail")
  streamed inline as autopilot walks.
- Walk-end cumulative tally appended to whatever final block fires.

No SU surcharge — parity with manual !harvest.

Pure helpers unit-tested (rarity classification, footer rendering,
walk tally sort order, rare-pending dedup). Full autoHarvestRoom
path needs prod DB and follows the existing setupAuditTestDB gating
pattern.

internal/plugin/dnd_zone_cmd.go

@@ -384,6 +384,8 @@ const (
 	stopEnded                      // patrol or room resolution killed the player
 	stopComplete                   // run cleared (boss down, no outgoing edges)
 	stopBlocked                    // an active CombatSession blocks the advance
+	stopRareNode                   // auto-harvest spotted a Rare+ node; player should decide
+	stopHarvestCombat              // auto-harvest pulled into combat that resolved short of death
 )
 
 // advanceResult bundles the staged narration + dispatch shape of one