N7/B2: Renown — prestige past the L20 cap

Overflow XP that grantDnDXP used to drop at L20 now accumulates as Renown
on player_meta.renown_xp (cumulative, atomic +=; renown_level derived as
renown_xp/25000). The reward is prestige-only: a derived rank ladder
(Renowned→…→Eternal), a cosmetic ✦N marker on the sheet and leaderboard,
a games-room shout on rank promotion, and !level progress once capped.

Renown perks are the two combat-neutral economy levers only — +loot / +XP,
capped at a streak-30 grant's economic half (+15% / +20%). combat_stats.go
reads DeathModifier/SuccessBonus/ExceptionalBonus (which map to Defense/
Attack/CritRate) but never LootQuality/XPMultiplier, so renown pays out even
through loadCombatBonuses without moving the golden or the balance corpus.
The plan's "-death penalty" perk is deliberately dropped (it would inflate
Defense).

The overflow→renown conversion and the character save commit in one
transaction (saveDnDCharacterExec now takes an executor), so a crash can
neither drop the overflow nor double-credit it on the next grant.

Schema: renown_xp column, DEFAULT 0 correct for every existing row, no
bootstrap (journal_pages/epilogue_cleared pattern).

Claude-Session: https://claude.ai/code/session_017mEwUmmS7aQTP2NQXj6rUa

internal/plugin/dnd_misc_cmds.go

@@ -161,6 +161,16 @@ func (p *AdventurePlugin) handleDnDLevelCmd(ctx MessageContext) error {
 	b.WriteString(fmt.Sprintf("⚔️ Level **%d** %s %s\n", c.Level, ri.Display, ci.Display))
 	if c.Level >= dndMaxLevel {
 		b.WriteString("XP: capped at L20.")
+		if rl := advChar.RenownLevel(); rl > 0 {
+			into, cost := renownXPIntoLevel(advChar.RenownXP)
+			b.WriteString(fmt.Sprintf("\n✦ **Renown %d**", rl))
+			if rank := renownRankFor(rl); rank != "" {
+				b.WriteString(fmt.Sprintf(" — _%s_", rank))
+			}
+			b.WriteString(fmt.Sprintf("\nRenown XP: %d / %d to Renown %d", into, cost, rl+1))
+		} else {
+			b.WriteString("\n_Overflow XP now earns **Renown** — prestige past the cap._")
+		}
 	} else {
 		next := dndXPToNextLevel(c.Level)
 		pct := int(100.0 * float64(c.XP) / float64(next))