Adv 2.0 Phase L2 step 4a: resolveArenaBoss helper

Adds resolveArenaBoss(userID, ArenaBossEncounter) — a single-round
combat path that routes through runZoneCombat + renderBossOutcome so
arena fights surface the same staged narration zone bosses use:
intro line, RenderCombatLog phases, Nat20/Nat1 mood lines, phase-two
barb on T3+ (ZoneArena routing), BossDeath/PlayerDeath flavor, dice
summary, arena-styled headline.

Behind ARENA_BOSS_FLOW env var (arenaBossFlowEnabled). Side-effect
free — no ArenaRun mutation, no payout, no history rows. The dispatch
into resolveArenaRound lands in step 4b once the surrounding economic
glue (rewards, achievements, helmet drops, death flag) is plumbed for
the new combat result shape.

Smoke tests cover (a) end-to-end arena round produces non-empty
intro/phases/outcome with the right headline, (b) bad tier/round
returns an error, (c) phase-two thresholds match the design doc,
(d) every tier×round arenaBosses entry has positive stats.

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

internal/plugin/adventure_arena_bossflow_test.go

@@ -0,0 +1,101 @@
+package plugin
+
+import (
+	"strings"
+	"testing"
+
+	"maunium.net/go/mautrix/id"
+)
+
+// Phase L2 step 4 — smoke test for resolveArenaBoss. Asserts the helper
+// returns staged narration (intro + phases + outcome) for a representative
+// arena round and that the outcome carries the boss-flow signatures: the
+// arena-styled headline and a dice-roll summary.
+
+func TestResolveArenaBoss_T1Round1_Smoke(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@arena-bossflow:example")
+	t.Cleanup(func() { cleanupZoneRuns(uid) })
+
+	if err := createAdvCharacter(uid, "bossflow"); err != nil {
+		t.Fatalf("createAdvCharacter: %v", err)
+	}
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceHuman, Class: ClassFighter, Level: 5,
+		STR: 18, DEX: 14, CON: 16, INT: 10, WIS: 10, CHA: 10,
+		HPMax: 60, HPCurrent: 60, ArmorClass: 18,
+	}
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatalf("SaveDnDCharacter: %v", err)
+	}
+
+	p := &AdventurePlugin{}
+	intro, phases, outcome, result, err := p.resolveArenaBoss(uid, ArenaBossEncounter{
+		Tier: 1, Round: 1, DisplayName: "Smoke",
+	})
+	if err != nil {
+		t.Fatalf("resolveArenaBoss: %v", err)
+	}
+	if intro == "" {
+		t.Error("intro empty")
+	}
+	if !strings.Contains(intro, "Arena T1 R1") {
+		t.Errorf("intro missing tier/round label: %q", intro)
+	}
+	if len(phases) == 0 {
+		t.Error("phases empty — combat log did not render")
+	}
+	if outcome == "" {
+		t.Error("outcome empty")
+	}
+	if result.PlayerWon {
+		// On a win the headline mentions "falls"; on a loss "stands over".
+		if !strings.Contains(outcome, "falls") {
+			t.Errorf("win outcome missing 'falls' headline: %q", outcome)
+		}
+	} else {
+		if !strings.Contains(outcome, "stands over") {
+			t.Errorf("loss outcome missing defeat headline: %q", outcome)
+		}
+	}
+}
+
+func TestResolveArenaBoss_BadTierRound(t *testing.T) {
+	setupAuditTestDB(t)
+	uid := id.UserID("@arena-bossflow-bad:example")
+	if err := createAdvCharacter(uid, "bad"); err != nil {
+		t.Fatalf("createAdvCharacter: %v", err)
+	}
+	p := &AdventurePlugin{}
+	if _, _, _, _, err := p.resolveArenaBoss(uid, ArenaBossEncounter{Tier: 9, Round: 9}); err == nil {
+		t.Error("expected error for unknown tier/round")
+	}
+}
+
+func TestArenaBossPhaseTwoAt(t *testing.T) {
+	cases := []struct {
+		tier int
+		want float64
+	}{{1, 0}, {2, 0}, {3, 0.5}, {4, 0.5}, {5, 0.5}}
+	for _, c := range cases {
+		if got := arenaBossPhaseTwoAt(c.tier); got != c.want {
+			t.Errorf("arenaBossPhaseTwoAt(%d)=%v want %v", c.tier, got, c.want)
+		}
+	}
+}
+
+func TestArenaBosses_AllTiersPopulated(t *testing.T) {
+	for tier := 1; tier <= 5; tier++ {
+		for round := 1; round <= 4; round++ {
+			id := arenaBossID(tier, round)
+			m, ok := arenaBosses[id]
+			if !ok {
+				t.Errorf("arenaBosses missing %s", id)
+				continue
+			}
+			if m.HP <= 0 || m.AC <= 0 || m.Attack <= 0 {
+				t.Errorf("%s has bad stats: HP=%d AC=%d ATK=%d", id, m.HP, m.AC, m.Attack)
+			}
+		}
+	}
+}