N4/E1: T3 housing payoffs + a home-rest "well-rested" buff

Turn the dead top housing tiers into something worth buying. All three
land without a schema bump, and TestCombatCharacterization stays
byte-identical (the balance corpus never sets the new fields).

T3 trophy room: treasure cap 3->4 at HouseTier>=3 (maxTreasuresForTier).
Enforced at the save gate only -- HouseTier is never written downward,
so a held 4th treasure below tier 3 is unreachable and a load-time cap in
computeAdvBonuses would just add a query for an impossible state. The
all-irreplaceable manual discard prompt now lists the 4th slot too.

T3 workshop: +5% craft success at HouseTier>=3, lifting the cap 0.95->0.98
so a maxed forager still gains. craftingSuccessRate takes a workshopBonus,
threaded through autoCraftConsumables and renderRecipesKnown.

Well-rested buff (replaces the plan's T4 "inn-quality rest", a verified
no-op -- home rest already equals inn rest). Home-only (the inn and a
tier-1 shack grant nothing), starts at T2 and grows through T4, expires at
the next long rest:
  - Temp HP cushion (8/12/16% of MaxHP). TempHP was a dormant field; wired
    into applyDnDHPScaling as MaxHP headroom -- additive and golden-safe.
  - Bonus spell slots (+1/+2/+3 at the caster's highest slot level), the
    real reward, lifting casters who trail on spell-pool richness.
    applyLongRestSpellSlots resets the pool to base then folds in the
    bonus; expiry is stateless (next rest's reset drops it).

Magnitudes are tunable defaults; revisit against the post-parties
re-baseline.

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

internal/plugin/dnd_rest.go

@@ -222,8 +222,15 @@ func (p *AdventurePlugin) handleDnDLongRest(ctx MessageContext) error {
 		innPaid = true
 	}
 
+	// Well-rested buff: only when resting at your own home (not the inn), and
+	// only from tier 2 up — a tier-1 shack and a rented inn room grant nothing.
+	restTier := 0
+	if hasHousing {
+		restTier = house.Tier
+	}
+
 	c.HPCurrent = c.HPMax
-	c.TempHP = 0
+	c.TempHP = wellRestedTempHP(c.HPMax, restTier)
 	c.ShortRestCharges = c.Level
 	// Phase 10 SUB2a — long rest clears one level of exhaustion (5e: a
 	// long rest clears one). For Berserker who racks up exhaustion via
@@ -241,8 +248,9 @@ func (p *AdventurePlugin) handleDnDLongRest(ctx MessageContext) error {
 	}
 	markActedToday(ctx.Sender)
 	_ = refreshAllResources(ctx.Sender)
-	// Phase 9: spell slots refresh on long rest.
-	_ = refreshSpellSlots(ctx.Sender)
+	// Phase 9: spell slots refresh on long rest. A home rest also folds in the
+	// well-rested bonus slots (no-op for non-casters and inn/tier-1 rests).
+	slotBonus, _ := applyLongRestSpellSlots(c, restTier)
 	// Phase 9: Cleric prep flags reset (SP4) — until SP4 ships, default
 	// Cleric grants are already prepared=1 so this is a no-op for them.
 	// Voluntary concentration ends at long rest (mage_armor's 8h is exactly
@@ -263,5 +271,13 @@ func (p *AdventurePlugin) handleDnDLongRest(ctx MessageContext) error {
 	if line := dndRestLongFlavorLine(hasHousing); line != "" {
 		msg += "\n\n_" + line + "_"
 	}
+	if bits := wellRestedSummary(c.TempHP, slotBonus); bits != "" {
+		homeName := "home"
+		if def := houseTierByTier(restTier); def != nil {
+			homeName = def.Name
+		}
+		msg += fmt.Sprintf("\n\n🛏️ _Well-rested at your %s — %s until your next long rest._",
+			strings.ToLower(homeName), bits)
+	}
 	return p.SendDM(ctx.Sender, msg)
 }