Address #127 review: quote the garden name, validate rectangles, require plantId

- The plan-name line of the system prompt interpolates the garden's name
  with %q like the rest of the prompt: any editor can rename a garden, and a
  name with a newline in it must not read as an instruction.
- fill_region refuses an inverted rectangle with its corners named, and a
  rectangle that misses the bed (or only touches its edge) is an error from
  the service rather than a successful fill of nothing.
- remove_plantings requires plantId; omitted it would remove plant 0 and
  report success.
- historyEntry.Undo → UndoOf (it holds the reverted change set's id).
- remove_planting's description names list_plantings as an id source.
- RemovePlanting takes the removal date itself; the dateless wrapper had no
  callers left.

Co-Authored-By: Claude Fable 5 <[email protected]>

internal/agent/tools.go

@@ -72,8 +72,8 @@ func NewToolbox(svc *service.Service, actorID int64, today string) *llm.Toolbox
 		llm.DefineTool("remove_planting",
 			"Remove ONE plop from a bed, leaving the rest — the single-plant answer to clear_object's "+
 				"all-or-nothing. Soft-removes it (kept for planting history, undoable), like clearing a "+
-				"bed does. Needs the plop's id and version from describe_garden. Use for \"pull the "+
-				"basil out of the corner\".",
+				"bed does. Needs the plop's id and version (describe_garden or list_plantings). Use "+
+				"for \"pull the basil out of the corner\".",
 			a.removePlanting),
 		llm.DefineTool("remove_plantings",
 			"Remove every plop of ONE plant from an object, leaving the other plants in it — \"take the "+
@@ -261,6 +261,9 @@ func (a *adapter) fillRegion(ctx context.Context, args struct {
 	}
 	switch {
 	case given == 4 && strings.TrimSpace(args.Region) == "":
+		if !(*args.X0CM < *args.X1CM && *args.Y0CM < *args.Y1CM) {
+			return nil, fmt.Errorf("%w: x0Cm must be west of x1Cm and y0Cm north of y1Cm (-y is north)", domain.ErrInvalidInput)
+		}
 		spec.Region = service.Region{MinX: *args.X0CM, MinY: *args.Y0CM, MaxX: *args.X1CM, MaxY: *args.Y1CM}
 	case given == 0 && strings.TrimSpace(args.Region) != "":
 		// the named region
@@ -352,6 +355,10 @@ func (a *adapter) removePlantings(ctx context.Context, args struct {
 	ObjectID int64 `json:"objectId" description:"object to remove the plant from"`
 	PlantID  int64 `json:"plantId" description:"the plant to remove every plop of (from describe_garden)"`
 }) (any, error) {
+	if args.PlantID == 0 {
+		// Left out, it would "remove" plant 0 — nothing — and report success.
+		return nil, fmt.Errorf("%w: plantId is required — say which plant to remove, or use clear_object for all of them", domain.ErrInvalidInput)
+	}
 	n, err := a.svc.ClearPlantings(ctx, a.actor, args.ObjectID,
 		service.ClearOptions{PlantID: &args.PlantID, RemovedAt: a.day("")})
 	if err != nil {
@@ -392,8 +399,8 @@ type historyEntry struct {
 	Summary string `json:"summary"`
 	Changes string `json:"changes"`
 	Undone  bool   `json:"undone,omitempty"`
-	// Undo is set when this entry is itself an undo of an earlier one.
-	Undo *int64 `json:"undoOf,omitempty"`
+	// UndoOf is the earlier entry this one reverted, when it is itself an undo.
+	UndoOf *int64 `json:"undoOf,omitempty"`
 }
 
 func (a *adapter) readHistory(ctx context.Context, args struct {
@@ -414,7 +421,7 @@ func (a *adapter) readHistory(ctx context.Context, args struct {
 		entries = append(entries, historyEntry{
 			ID: cs.ID, When: cs.CreatedAt, Source: cs.Source, Who: cs.ActorName,
 			Summary: cs.Summary, Changes: describeCounts(cs.Counts),
-			Undone: cs.RevertedByID != nil, Undo: cs.RevertsID,
+			Undone: cs.RevertedByID != nil, UndoOf: cs.RevertsID,
 		})
 	}
 	return map[string]any{"entries": entries, "hasMore": hasMore}, nil
@@ -467,7 +474,7 @@ func (a *adapter) removePlanting(ctx context.Context, args struct {
 }) (any, error) {
 	// Soft-remove via the service, dated the gardener's local day like every
 	// other tool here (the service clock's UTC day when that isn't known).
-	return a.svc.RemovePlantingOn(ctx, a.actor, args.PlantingID, args.Version, a.day(""))
+	return a.svc.RemovePlanting(ctx, a.actor, args.PlantingID, args.Version, a.day(""))
 }
 
 func (a *adapter) listSeedLots(ctx context.Context, args struct {