Agent: what a day of live use asked for

Twenty-one prompts against the live assistant found one fabricated success,
a model that believed it was 2025, and a describe_garden that was ~450 plop
entries per turn. This is the set of fixes, each traceable to a finding:

- The gardener's LOCAL day travels with the turn (`today` on POST /agent/chat,
  sent by the UI like plantedAt) into the system prompt and every dated tool
  default. Left to guess, the model dated journal entries a year back; left to
  the server, a 9 pm fill landed on UTC's tomorrow.
- describe_garden groups plops by plant — count, where, planted date, days to
  maturity — and lists ids only for groups of ≤ 8; list_plantings spells a big
  group out on demand and remove_plantings acts on one plant in a bed ("take
  the beets out, leave the garlic"), which used to mean 116 single removals.
- New tools: move_planting (keeps the planting date; across beds via the new
  MovePlanting, which is why the store's UPDATE now writes object_id),
  update_plant, read_history, copy_garden (the "<garden> — <year>" plan
  convention). fill_region takes an explicit local rectangle and a seedLotId;
  place_planting's radius defaults to one plant (spacing/2) instead of a guess.
- The system prompt states the date and the gardener's units, forbids claiming
  a change no tool made, says it cannot undo and points at the Undo button,
  asks before clearing beds on an ambiguous sentence, and stops narrating its
  own plantings into the journal.
- A mutation aimed at ANOTHER garden inside a turn is recorded under that
  garden as its own change set, not filed into the open scope.
- UI: the thread scrolls inside the Assistant panel so the composer stays
  put; every tool has a step label; wide tables stay inside the bubble.

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

CLAUDE.md

@@ -160,6 +160,24 @@ Conventions that follow from it:
   plantings. Fixing it per-call-site is how it came back, which is why the rule
   lives in `commitScope` where no caller can forget it.
 
+- **The assistant's date comes from the client, never from the model.**
+  `POST /agent/chat` carries `today` (the browser's local day, same reason the
+  UI sends `plantedAt`); `Runner.Run` puts it in the system prompt and
+  `NewToolbox` stamps it on every dated tool default through `adapter.day`. A
+  new tool that takes a date defaults through `day()`, not `time.Now()`. Left to
+  guess, the live model dated journal entries a year back (2025) — the year it
+  remembered from training.
+- **`describe_garden` is a summary, not a dump.** Plops are grouped per plant
+  (`service.DescribeGroup`: count, where, planted date, days to maturity) and
+  ids are listed only for groups of ≤ `maxListedPlops`; the first grid-filled
+  garden made the old per-plop describe ~450 entries on every turn. A tool that
+  needs individual ids uses `list_plantings`; bulk work takes (object, plant)
+  — `remove_plantings`, `ClearPlantings`. Don't add a tool that lists plops.
+- **The assistant can't undo and must not pretend to.** Asked to "undo the
+  beets", the live model replied "Done!" and changed nothing. The prompt now
+  forbids claiming a change no tool made and points at the Undo button; keep
+  both rules when editing `systemPrompt`.
+
 - **Request deadlines are extended through `responseController(c)`, never
   `http.NewResponseController(c.Writer)`.** A controller built in a handler
   can't reach the socket — the logging middleware wraps the writer — so every