Adv 2.0 D&D polish: GM→DM rename, streamed zone combat, end-to-end scenario test

GM→DM rename across docs and code (GMNarrationType→DMNarrationType,
GMState→DMState, narration constants, comments) so the system reads as
"Dungeon Master" everywhere. Player-visible "GM mood" wording stays
where it appears in flavor.

Streamed zone/expedition combat: zone advance now stages patrol →
patrol play-by-play → patrol resolution → room intro → room play-by-play
→ final outcome through sendZoneCombatMessages with 2–3s pacing
(arena keeps its 5–8s window). Combat narrative lines pick up a compact
d20-vs-AC roll annotation for hit/crit/miss/block events.

Combat outcome polish: dndHPSnapshot lets narration show sheet HP
rather than legacy combat-engine HP, and markAdventureDead clears the
zombie state where hp_current was 0 but the legacy alive flag stayed
true after a D&D-layer KO.

Adv 2.0 announcement (ADVENTURE_2.0_ANNOUNCEMENT.md), README rewrite
covering the new layer, and adv2_scenario_test.go — a full
zone-run + expedition + harvest playthrough against a copy of the prod
DB asserting persisted state end-to-end.

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

internal/plugin/dnd_cast.go

@@ -145,10 +145,12 @@ func (p *AdventurePlugin) handleDnDCastCmd(ctx MessageContext, args string) erro
 		}
 	}
 
-	// Reaction spells deferred.
+	// Reaction spells deferred — combat is one-shot SimulateCombat, no
+	// per-turn windows where a reaction could trigger. Will land alongside
+	// turn-based combat when that arrives.
 	if spell.Effect == EffectReaction {
 		return p.SendDM(ctx.Sender, fmt.Sprintf(
-			"%s is a reaction spell — those land in Phase 11 alongside turn-based boss combat.", spell.Name))
+			"%s is a reaction spell — those aren't usable yet (combat resolves in one beat, no reaction window). Pick a different spell.", spell.Name))
 	}
 
 	// Known + prepared check.