Adv 2.0 D&D Phase R R2: Harvest nodes & per-room registry

Per-zone resource registry (§3, all 10 zones) and full per-room harvest
layer wired into expeditions: !forage / !mine / !scavenge / !essence /
!commune / !resources. Auto-spawns a DungeonRun per region on
!expedition start, swaps it on !region travel, retires on
abandon/extract. Long rest at camp replenishes nodes across every
room and region. Reuses existing flavor.Harvest* / RichYield /
NodeDepleted / per-zone Harvest<Zone> pools.

Also clears two pre-existing test failures introduced by the E6c
flavor expansion (briefing substring list + combat-lift trial count).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/plugin/dnd_equipment.go

@@ -64,6 +64,7 @@ const (
 	RarityUncommon  DnDRarity = "Uncommon"
 	RarityRare      DnDRarity = "Rare"
 	RarityEpic      DnDRarity = "Epic"
+	RarityVeryRare  DnDRarity = "VeryRare"
 	RarityLegendary DnDRarity = "Legendary"
 )