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/adventure_render.go

@@ -1037,8 +1037,17 @@ func renderAdvLeaderboard(chars []AdvLeaderboardEntry) string {
 // ── Treasure Discard Prompt ──────────────────────────────────────────────────
 
 func renderAdvTreasureDiscardPrompt(newTreasure *AdvTreasureDef, existing []AdvTreasureDef) string {
-	if len(TreasureInventoryCap) == 0 {
-		return "You found a treasure but your inventory is full. Reply 1, 2, or 3 to discard, or `keep`."
+	// The flavor templates below are written for the base 3-slot set. With a
+	// T3 trophy room the set can hold 4, so fall back to a plain dynamic list
+	// whenever it isn't exactly 3 — every slot has to be visible to choose it.
+	if len(TreasureInventoryCap) == 0 || len(existing) != 3 {
+		var b strings.Builder
+		fmt.Fprintf(&b, "You found **%s** but your treasure slots are full. Discard one to make room:\n", newTreasure.Name)
+		for i, ex := range existing {
+			fmt.Fprintf(&b, "%d. %s — %s\n", i+1, ex.Name, ex.InventoryDesc)
+		}
+		fmt.Fprintf(&b, "\nReply with the number to discard, or `keep` to leave the new one behind.")
+		return b.String()
 	}
 
 	// Build substitution map with existing treasure info