Address Gadfly review on #10: clearable color/props, column lists, dedup

Fixes from the PR #28 adversarial review (considered; not graded).

Correctness / API
- PATCH /objects/:id can now clear nullable color/props back to NULL: the
  request takes them as json.RawMessage, and ObjectPatch carries an explicit
  Set flag so an explicit `null` (clear) is distinguished from an absent
  field (unchanged) — the strongest cross-model finding (6 hits). New test.

Maintainability
- store/plantings.go + plants.go use explicit qualified column lists
  (qualifyColumns helper) instead of SELECT *, matching gardens/objects and
  surviving a future column add.
- Consolidated objectKinds + plantableByDefault into one kind→traits map.
- objectForRole factors the fetch-then-authorize shared by UpdateObject and
  DeleteObject; dropped the redundant kind check in CreateObject
  (finalizeObject is the single validation point).
- Request→service mapping via toInput()/toPatch() methods (matches gardens).
- Renamed handler gardenFull → getGardenFull (verbNoun); test helper
  decodeGarden → decodeMap; generic bind-error messages.

Co-Authored-By: Claude Opus 4.8 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01JdQpdYYsTgtkJBxbcpAszi

internal/api/objects.go

@@ -30,9 +30,19 @@ type objectCreateRequest struct {
 	Notes       string          `json:"notes"`
 }
 
+func (r objectCreateRequest) toInput() service.ObjectInput {
+	return service.ObjectInput{
+		Kind: r.Kind, Name: r.Name, Shape: r.Shape,
+		XCM: r.XCM, YCM: r.YCM, WidthCM: r.WidthCM, HeightCM: r.HeightCM,
+		RotationDeg: r.RotationDeg, ZIndex: r.ZIndex, Plantable: r.Plantable,
+		Color: r.Color, Props: propsFromRaw(r.Props), Notes: r.Notes,
+	}
+}
+
 // objectUpdateRequest is the body for PATCH /objects/:id: every field optional
 // (absent = unchanged), plus the required current version. Kind and shape are
-// immutable and not accepted.
+// immutable and not accepted. color/props are json.RawMessage so an explicit
+// null (clear the override) is distinguishable from an absent field (unchanged).
 type objectUpdateRequest struct {
 	Name        *string         `json:"name"`
 	XCM         *float64        `json:"xCm"`
@@ -42,20 +52,60 @@ type objectUpdateRequest struct {
 	RotationDeg *float64        `json:"rotationDeg"`
 	ZIndex      *int            `json:"zIndex"`
 	Plantable   *bool           `json:"plantable"`
-	Color       *string         `json:"color"`
+	Color       json.RawMessage `json:"color"`
 	Props       json.RawMessage `json:"props"`
 	Notes       *string         `json:"notes"`
 	Version     int64           `json:"version" binding:"required,min=1"`
 }
 
-// propsFromRaw maps a JSON props value to the stored *string: a present, non-null
-// value becomes its JSON text; absent or null becomes nil (leave/none).
+func (r objectUpdateRequest) toPatch() (service.ObjectPatch, error) {
+	color, setColor, err := parseNullableString(r.Color)
+	if err != nil {
+		return service.ObjectPatch{}, err
+	}
+	props, setProps := parseNullableJSON(r.Props)
+	return service.ObjectPatch{
+		Name: r.Name, XCM: r.XCM, YCM: r.YCM, WidthCM: r.WidthCM, HeightCM: r.HeightCM,
+		RotationDeg: r.RotationDeg, ZIndex: r.ZIndex, Plantable: r.Plantable,
+		SetColor: setColor, Color: color, SetProps: setProps, Props: props, Notes: r.Notes,
+	}, nil
+}
+
+// propsFromRaw maps a JSON props value to the stored *string for create: a
+// present, non-null value becomes its JSON text; absent or null becomes nil.
 func propsFromRaw(raw json.RawMessage) *string {
-	if len(raw) == 0 || string(raw) == "null" {
+	v, set := parseNullableJSON(raw)
+	if !set {
 		return nil
 	}
+	return v
+}
+
+// parseNullableString decodes a JSON string|null field into (value, present).
+// Absent → (nil, false); null → (nil, true); "x" → (&"x", true). A non-string
+// value is an error.
+func parseNullableString(raw json.RawMessage) (value *string, present bool, err error) {
+	if len(raw) == 0 {
+		return nil, false, nil
+	}
+	if err := json.Unmarshal(raw, &value); err != nil {
+		return nil, false, err
+	}
+	return value, true, nil
+}
+
+// parseNullableJSON decodes any JSON value into (text, present) for a nullable
+// TEXT column. Absent → (nil, false); null → (nil, true); anything else → the
+// raw JSON text (&, true).
+func parseNullableJSON(raw json.RawMessage) (value *string, present bool) {
+	if len(raw) == 0 {
+		return nil, false
+	}
+	if string(raw) == "null" {
+		return nil, true
+	}
 	s := string(raw)
-	return &s
+	return &s, true
 }
 
 func (h *handlers) createObject(c *gin.Context) {
@@ -65,24 +115,10 @@ func (h *handlers) createObject(c *gin.Context) {
 	}
 	var req objectCreateRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
-		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "kind is required")
+		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "invalid object: kind is required")
 		return
 	}
-	o, err := h.svc.CreateObject(c.Request.Context(), mustActor(c).ID, gardenID, service.ObjectInput{
-		Kind:        req.Kind,
-		Name:        req.Name,
-		Shape:       req.Shape,
-		XCM:         req.XCM,
-		YCM:         req.YCM,
-		WidthCM:     req.WidthCM,
-		HeightCM:    req.HeightCM,
-		RotationDeg: req.RotationDeg,
-		ZIndex:      req.ZIndex,
-		Plantable:   req.Plantable,
-		Color:       req.Color,
-		Props:       propsFromRaw(req.Props),
-		Notes:       req.Notes,
-	})
+	o, err := h.svc.CreateObject(c.Request.Context(), mustActor(c).ID, gardenID, req.toInput())
 	if err != nil {
 		writeServiceError(c, err)
 		return
@@ -97,22 +133,15 @@ func (h *handlers) updateObject(c *gin.Context) {
 	}
 	var req objectUpdateRequest
 	if err := c.ShouldBindJSON(&req); err != nil {
-		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "a current version is required")
+		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "invalid update: a current version is required")
 		return
 	}
-	o, err := h.svc.UpdateObject(c.Request.Context(), mustActor(c).ID, id, service.ObjectPatch{
-		Name:        req.Name,
-		XCM:         req.XCM,
-		YCM:         req.YCM,
-		WidthCM:     req.WidthCM,
-		HeightCM:    req.HeightCM,
-		RotationDeg: req.RotationDeg,
-		ZIndex:      req.ZIndex,
-		Plantable:   req.Plantable,
-		Color:       req.Color,
-		Props:       propsFromRaw(req.Props),
-		Notes:       req.Notes,
-	}, req.Version)
+	patch, err := req.toPatch()
+	if err != nil {
+		writeAPIError(c, http.StatusBadRequest, "INVALID_INPUT", "invalid update payload")
+		return
+	}
+	o, err := h.svc.UpdateObject(c.Request.Context(), mustActor(c).ID, id, patch, req.Version)
 	if err != nil {
 		if errors.Is(err, domain.ErrVersionConflict) {
 			writeVersionConflict(c, o)
@@ -136,7 +165,7 @@ func (h *handlers) deleteObject(c *gin.Context) {
 	c.Status(http.StatusNoContent)
 }
 
-func (h *handlers) gardenFull(c *gin.Context) {
+func (h *handlers) getGardenFull(c *gin.Context) {
 	gardenID, ok := parseIDParam(c, "id")
 	if !ok {
 		return