H5: partial spell-slot refresh on short rest

Short rest now restores all L1 slots plus floor(level/4) additional slots
at the next-available tier ≥L2, lowest-first. Long rest still does a full
wipe; martials and full-pool casters see no DM change.

internal/plugin/dnd_rest_test.go

@@ -146,6 +146,139 @@ func TestShortRest_AlreadyFullHP(t *testing.T) {
 	}
 }
 
+// makeRestTestMage builds a wounded mage (so short rest doesn't bail on
+// full-HP) and provisions the class slot pool. The caller is responsible
+// for burning slots before testing the refresh.
+func makeRestTestMage(t *testing.T, uid id.UserID, level int) *DnDCharacter {
+	t.Helper()
+	c := &DnDCharacter{
+		UserID: uid, Race: RaceHuman, Class: ClassMage, Level: level,
+		STR: 8, DEX: 13, CON: 12, INT: 16, WIS: 10, CHA: 12,
+	}
+	conMod := abilityModifier(c.CON)
+	c.HPMax = computeMaxHP(c.Class, conMod, level)
+	c.HPCurrent = 1
+	c.ArmorClass = computeAC(c.Class, abilityModifier(c.DEX))
+	c.ShortRestCharges = level
+	if err := SaveDnDCharacter(c); err != nil {
+		t.Fatal(err)
+	}
+	if err := createAdvCharacter(uid, "mage_rest_test"); err != nil {
+		t.Fatal(err)
+	}
+	if err := setSpellSlotsForLevel(uid, ClassMage, level); err != nil {
+		t.Fatal(err)
+	}
+	return c
+}
+
+func TestPartialRefreshSpellSlots_L5MageToPsAtL2(t *testing.T) {
+	setupRestTestDB(t)
+	uid := id.UserID("@partial_l5:example")
+	makeRestTestMage(t, uid, 5) // L5 mage → 4 L1, 3 L2, 2 L3
+
+	// Burn everything so the refresh has work to do.
+	pool := slotsForClassLevel(ClassMage, 5)
+	for lvl, total := range pool {
+		for i := 0; i < total; i++ {
+			if _, err := consumeSpellSlot(uid, lvl); err != nil {
+				t.Fatal(err)
+			}
+		}
+	}
+
+	restored, err := partialRefreshSpellSlots(uid, 5)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got := restored[1]; got != pool[1] {
+		t.Errorf("L1 restored = %d, want %d (all)", got, pool[1])
+	}
+	if got := restored[2]; got != 1 {
+		t.Errorf("L2 restored = %d, want 1 (floor(5/4))", got)
+	}
+	if _, ok := restored[3]; ok {
+		t.Errorf("L3 should not have been restored: %v", restored)
+	}
+
+	slots, _ := getSpellSlots(uid)
+	if used := slots[1][1]; used != 0 {
+		t.Errorf("L1 used after refresh = %d, want 0", used)
+	}
+	if used := slots[2][1]; used != pool[2]-1 {
+		t.Errorf("L2 used after refresh = %d, want %d", used, pool[2]-1)
+	}
+	if used := slots[3][1]; used != pool[3] {
+		t.Errorf("L3 used after refresh = %d, want %d (untouched)", used, pool[3])
+	}
+}
+
+func TestPartialRefreshSpellSlots_NonCasterNoop(t *testing.T) {
+	setupRestTestDB(t)
+	uid := id.UserID("@partial_fighter:example")
+	makeRestTestChar(t, uid, 5) // fighter — no slots
+
+	restored, err := partialRefreshSpellSlots(uid, 5)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if restored != nil {
+		t.Errorf("fighter got slots restored: %v", restored)
+	}
+}
+
+func TestPartialRefreshSpellSlots_FullCasterReturnsEmpty(t *testing.T) {
+	setupRestTestDB(t)
+	uid := id.UserID("@partial_full:example")
+	makeRestTestMage(t, uid, 5) // slots already at used=0 from setup
+
+	restored, err := partialRefreshSpellSlots(uid, 5)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if restored != nil {
+		t.Errorf("full mage got slots restored: %v", restored)
+	}
+}
+
+func TestShortRest_RefreshesPartialSlotsForMage(t *testing.T) {
+	setupRestTestDB(t)
+	uid := id.UserID("@short_mage:example")
+	makeRestTestMage(t, uid, 5)
+	pool := slotsForClassLevel(ClassMage, 5)
+	for lvl, total := range pool {
+		for i := 0; i < total; i++ {
+			consumeSpellSlot(uid, lvl)
+		}
+	}
+
+	p := &AdventurePlugin{}
+	if err := p.handleDnDShortRest(MessageContext{Sender: uid}); err != nil {
+		t.Fatal(err)
+	}
+	slots, _ := getSpellSlots(uid)
+	if used := slots[1][1]; used != 0 {
+		t.Errorf("L1 used after short rest = %d, want 0", used)
+	}
+	if used := slots[2][1]; used != pool[2]-1 {
+		t.Errorf("L2 used after short rest = %d, want %d", used, pool[2]-1)
+	}
+}
+
+func TestDndShortRestSlotLine(t *testing.T) {
+	if got := dndShortRestSlotLine(nil); got != "" {
+		t.Errorf("nil → %q, want empty", got)
+	}
+	if got := dndShortRestSlotLine(map[int]int{}); got != "" {
+		t.Errorf("empty → %q, want empty", got)
+	}
+	got := dndShortRestSlotLine(map[int]int{1: 4, 2: 1})
+	want := "Spell slots restored: 4 (L1), 1 (L2)."
+	if got != want {
+		t.Errorf("got %q, want %q", got, want)
+	}
+}
+
 func TestLongRest_RequiresHousingOrInn(t *testing.T) {
 	setupRestTestDB(t)
 	uid := id.UserID("@long_no_house:example")