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_subclass_cmd.go

@@ -150,7 +150,6 @@ func (p *AdventurePlugin) applySubclassChoice(
 		b.WriteString(fmt.Sprintf("_%d euros spent. Cooldown: %dd before next change._\n\n",
 			dndSubclassRespecCost, int(dndSubclassRespecCooldown/(24*time.Hour))))
 	}
-	b.WriteString("_" + info.Flavor + "_\n\n")
-	b.WriteString("_(Mechanical L5/7/10/15 subclass abilities land in upcoming phases.)_")
+	b.WriteString("_" + info.Flavor + "_")
 	return p.SendDM(ctx.Sender, b.String())
 }