Smoke-sweep fixes: exact saves, local dates, safer remove, readable markers

- Garden and plant dialogs keep centimeters as the source of truth
  (LengthField in lib/units.ts): a no-change Save no longer rewrites
  900 cm as 899.922 or a 45 cm spacing as 44.958, bumping versions and
  writing bogus history entries on the way.
- The UI stamps every date with the browser's local day (lib/dates.ts).
  Journal notes already did; plop placement, fill and removal now do too,
  so a 9 pm placement isn't "planted tomorrow". The fill endpoint gained an
  optional plantedAt; API and agent callers still default to UTC today.
- Removing an object that holds plants asks first and says how many go
  with it. An empty one still goes straight away (one Undo restores it).
- The expanded plant card's action row wraps instead of clipping "Delete".
- Monogram lettering switches to a dark ink on pale marker colors (garlic,
  cabbage, marigold) instead of near-white on near-white.
- Copy-as-plan proposes the next free year and warns when the typed name
  already exists, so two gardens can't both read as "the 2027 plan".
- Plan cards show the base name with a "2027 plan" tag, so the year — the
  point of the name — survives truncation.
- A rejected model spec now says which model and why: a wrapped
  ErrInvalidInput's reason reaches the client as the 400's message, and the
  Settings field shows it inline instead of toasting "invalid input".

Also defuses a clock bomb in TestRemainingReturnsWhenAPlantingIsRemoved,
which only passed while the real date was before 2026-08-01.

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

internal/service/ops.go

@@ -175,13 +175,15 @@ func validFillLayout(l FillLayout) (FillLayout, bool) {
 // in from each edge by edgeInset — a half-spacing for grid, radius-less-a-half-
 // spacing for a clump (see edgeInset for the why). A candidate is skipped when its
 // plop would sit entirely inside an existing active plop (so re-filling doesn't
-// stack duplicates). Returns the plops it created.
-func (s *Service) FillRegion(ctx context.Context, actorID, objectID int64, region Region, plantID int64, spacingOverride *float64, layout FillLayout) ([]domain.Planting, error) {
+// stack duplicates). Every plop is dated plantedAt (YYYY-MM-DD), or UTC today
+// when nil — the UI always sends its local day, so the default is for API and
+// agent callers. Returns the plops it created.
+func (s *Service) FillRegion(ctx context.Context, actorID, objectID int64, region Region, plantID int64, spacingOverride *float64, layout FillLayout, plantedAt *string) ([]domain.Planting, error) {
 	o, _, err := s.objectForRole(ctx, actorID, objectID, roleEditor)
 	if err != nil {
 		return nil, err
 	}
-	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride, layout)
+	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride, layout, plantedAt)
 }
 
 // fillLoaded is the shared body of FillRegion/FillNamedRegion given an object
@@ -189,10 +191,13 @@ func (s *Service) FillRegion(ctx context.Context, actorID, objectID int64, regio
 // non-finite region, clamps the region to the object's bounds, refuses fills over
 // maxFillPlops, and inserts the whole batch in one transaction rather than one
 // round-trip per plop.
-func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.GardenObject, region Region, plantID int64, spacingOverride *float64, layout FillLayout) ([]domain.Planting, error) {
+func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.GardenObject, region Region, plantID int64, spacingOverride *float64, layout FillLayout, plantedAt *string) ([]domain.Planting, error) {
 	if !o.Plantable {
 		return nil, domain.ErrInvalidInput
 	}
+	if !validDatePtr(plantedAt) {
+		return nil, fmt.Errorf("%w: plantedAt must be a YYYY-MM-DD date", domain.ErrInvalidInput)
+	}
 	layout, ok := validFillLayout(layout)
 	if !ok {
 		return nil, domain.ErrInvalidInput
@@ -235,7 +240,10 @@ func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.Garde
 	if err != nil {
 		return nil, err
 	}
-	today := s.now().UTC().Format(dateLayout)
+	plantedOn := s.now().UTC().Format(dateLayout)
+	if plantedAt != nil {
+		plantedOn = *plantedAt
+	}
 	batch := make([]*domain.Planting, 0, len(centers))
 	// Only the plops that were ALREADY here can cover a candidate: every plop this
 	// fill makes shares one radius and sits on a distinct lattice point, and a plop
@@ -247,7 +255,7 @@ func (s *Service) fillLoaded(ctx context.Context, actorID int64, o *domain.Garde
 		if coveredByExisting(c.x, c.y, radius, existing) {
 			continue
 		}
-		batch = append(batch, &domain.Planting{ObjectID: o.ID, PlantID: plantID, XCM: c.x, YCM: c.y, RadiusCM: radius, PlantedAt: &today})
+		batch = append(batch, &domain.Planting{ObjectID: o.ID, PlantID: plantID, XCM: c.x, YCM: c.y, RadiusCM: radius, PlantedAt: &plantedOn})
 	}
 	created, err := s.store.CreatePlantings(ctx, batch)
 	if err != nil {
@@ -376,7 +384,7 @@ func coveredByExisting(x, y, radius float64, existing []domain.Planting) bool {
 // FillNamedRegion is FillRegion addressed by a compass name ("ne", "south half")
 // instead of a resolved Region — the ergonomic form for agent tools, which don't
 // hold the object's geometry. It resolves the name against the object, then fills.
-func (s *Service) FillNamedRegion(ctx context.Context, actorID, objectID int64, regionName string, plantID int64, spacingOverride *float64, layout FillLayout) ([]domain.Planting, error) {
+func (s *Service) FillNamedRegion(ctx context.Context, actorID, objectID int64, regionName string, plantID int64, spacingOverride *float64, layout FillLayout, plantedAt *string) ([]domain.Planting, error) {
 	o, _, err := s.objectForRole(ctx, actorID, objectID, roleEditor)
 	if err != nil {
 		return nil, err
@@ -385,7 +393,7 @@ func (s *Service) FillNamedRegion(ctx context.Context, actorID, objectID int64,
 	if err != nil {
 		return nil, err
 	}
-	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride, layout)
+	return s.fillLoaded(ctx, actorID, o, region, plantID, spacingOverride, layout, plantedAt)
 }
 
 // ClearObject soft-removes every active plop in an object the actor can edit (one