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/agent/runtime_test.go

@@ -60,7 +60,7 @@ func TestTurnIsOneChangeSet(t *testing.T) {
 	if err != nil {
 		t.Fatalf("bed: %v", err)
 	}
-	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil, service.FillClump); err != nil {
+	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil, service.FillClump, nil); err != nil {
 		t.Fatalf("seed garlic: %v", err)
 	}
 

internal/agent/tools.go

@@ -163,7 +163,9 @@ func (a *adapter) fillRegion(ctx context.Context, args struct {
 	SpacingOverride *float64 `json:"spacingOverrideCm" description:"optional in-row spacing override in cm; omit to use the plant's spacing"`
 	Mode            string   `json:"mode" enum:"clump,grid" description:"clump (default) drops a few fat clumps for a quick sketch; grid lays out individual plants in rows at true spacing, a layout you could plant from"`
 }) (any, error) {
-	return a.svc.FillNamedRegion(ctx, a.actor, args.ObjectID, args.Region, args.PlantID, args.SpacingOverride, service.FillLayout(args.Mode))
+	// nil: the agent runs server-side with no local day, so the fill dates
+	// plops UTC-today like its create_planting does.
+	return a.svc.FillNamedRegion(ctx, a.actor, args.ObjectID, args.Region, args.PlantID, args.SpacingOverride, service.FillLayout(args.Mode), nil)
 }
 
 func (a *adapter) findPlant(ctx context.Context, args struct {

internal/agent/tools_test.go

@@ -169,7 +169,7 @@ func TestGarlicBedToCucumbers(t *testing.T) {
 	if err != nil {
 		t.Fatalf("bed: %v", err)
 	}
-	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil, service.FillClump); err != nil {
+	if _, err := svc.FillNamedRegion(ctx, owner, bed.ID, "all", garlic.ID, nil, service.FillClump, nil); err != nil {
 		t.Fatalf("seed the garlic: %v", err)
 	}