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/revisions_test.go

@@ -73,7 +73,7 @@ func TestFillRegionIsOneChangeSet(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	created, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump)
+	created, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump, nil)
 	if err != nil {
 		t.Fatalf("FillNamedRegion: %v", err)
 	}
@@ -320,7 +320,7 @@ func TestRevertClearObject(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
+	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump, nil); err != nil {
 		t.Fatalf("fill: %v", err)
 	}
 	before, _ := s.store.ListActivePlantingsForObject(ctx, bed.ID)
@@ -688,7 +688,7 @@ func TestClearObjectOnlyClearsWhatItSnapshotted(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
+	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump, nil); err != nil {
 		t.Fatalf("fill: %v", err)
 	}
 	before, _ := s.store.ListActivePlantingsForObject(ctx, bed.ID)
@@ -725,7 +725,7 @@ func TestRevertResultCarriesItsCounts(t *testing.T) {
 	plant := seedOwnPlant(t, s, owner, 15)
 	ctx := context.Background()
 
-	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
+	if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump, nil); err != nil {
 		t.Fatalf("fill: %v", err)
 	}
 	// A second, different kind of change, so the breakdown has more than one row
@@ -830,7 +830,7 @@ func TestSucceededTurnRecordsEvenIfTheCallerWentAway(t *testing.T) {
 	cs, err := s.WithChangeSet(ctx, owner, g.ID, ChangeSetOptions{
 		Source: domain.SourceAgent, Summary: "plant beans in the second bed",
 	}, func(ctx context.Context) error {
-		if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump); err != nil {
+		if _, err := s.FillNamedRegion(ctx, owner, bed.ID, "all", plant.ID, nil, FillClump, nil); err != nil {
 			return err
 		}
 		cancel() // the client disconnects, mid-turn, after the work landed