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]>

web/src/lib/dates.ts

@@ -0,0 +1,11 @@
+// The day it is where the person is. Everything the UI stamps with "today" — a
+// journal note, a placed or filled plant — uses the browser's local date,
+// because a gardener planting at 9 pm in Ohio planted today, not (in UTC)
+// tomorrow. The server's own defaults are UTC and only apply when a date is
+// omitted, which is for API callers and the agent; the UI never omits one.
+
+/** Today as YYYY-MM-DD in the browser's local time zone. */
+export function today(now = new Date()): string {
+  const pad = (n: number) => String(n).padStart(2, '0')
+  return `${now.getFullYear()}-${pad(now.getMonth() + 1)}-${pad(now.getDate())}`
+}