* fix(app,dash): render pre-history days as no data, not a currency zero
Days before the first recorded day in history.daily were painted as a real
0.00/0 calls in the daily activity heatmap and the daily spend charts. That
zero is unknown, not measured, so those cells and bars now read "No data
recorded" instead of a currency zero. Genuinely idle days within recorded
history stay as real zeros.
- app: heatmap cells, the daily spend bars, and the daily-by-model columns
get a distinct no-data style plus a "No data recorded" hover for days before
the first recorded day.
- dash: the granular line chart drops buckets before the first recorded day so
no flat zero line is drawn before any history exists.
- data-start is derived in the UI layer from history.daily; payload shape is
unchanged.
Verified: app vitest 418 pass (7 new for the no-data behavior); app, dash, and
root typecheck clean; dash and app renderer vite builds succeed.
* no-data: cap guard, timezone-free dash trim, StackedBars aria
Three hardening fixes from adversarial review of the no-data rendering:
dataStartKey returns null at the payload's 365-entry history cap, where
the oldest retained entry is no longer the true data start; classifying
past it would label real aged-out history as no data on long custom
ranges. Documented that the install-to-first-use gap reading as no data
is literally accurate: nothing was recorded then either.
The dash granular chart now trims leading zero-only buckets by value
instead of comparing bucket timestamps against date keys, so producer
and viewer timezone skew can never drop a real first-day bucket, and an
all-zero series lands in the established empty state.
StackedBars no-data columns expose their state via aria-label, not only
a title on a non-focusable div.
Per feedback, the hero (number + KPIs) and the git-style daily-activity
heatmap now share a single card, split left/right with a divider.
ActivityHeatmap gains a 'bare' mode (renders head+grid without its own
card wrapper). Efficiency scorecard + fuel ring move to a row below.
