dash: the first savings bar renders 158% in a 100%-wide track — a ratio presented as a share

[amiddavid]

The first figure on the dashboard overview — the top bar under "Savings percentage — four
denominators, four questions" — renders 158.17% in a track that is 100% wide by
construction, so the bar is pinned full while the number beside it says otherwise.

main        pct=115.42  available=True
PR #138     pct=158.17  available=True     409k ÷ 259k tokens

Cause

renderDenominators (dash/ui/app.js:489) passes max: 100 and value: d.percent, so a
percent above 100 clips:

value: d.available ? d.percent : 0,
max: 100,
display: d.available ? pct(d.percent, 2) : 'n/a',

The arithmetic is intended, and documented at docs/dashboard.md:80: the numerator is gross
savings while attempted_tokens is re-counted every turn, so the quotient is a ratio and can
exceed 1. Only the presentation is wrong — a figure over 100% under a heading "Savings
percentage", rendered as a share of a full track, reads as a bug to anyone who has not read
that paragraph, and it is the first thing on the page.

Why now

It gets worse as the product gets better. PR #138 teaches collapse to cut single-line and
huge-line payloads it used to decline, which pushes this figure from 115% to 158% on the same
traffic. Measured by a dashboard agent driving the live UI (headless Chromium, real proxy, real
traffic) against both builds. It is pre-existing, and #138 does not touch dash/ — but #138 is
what moves it past the point where a reader can charitably ignore it.

Fix options

1. Render a ratio when it is one — 1.58× with the track at min(1, percent/100), keeping
   % for the denominators that genuinely are shares. Preserves the bar as a visual and stops
   it contradicting its own label. Recommended.
2. Drop the track for this row and show the bare figure with its divisor
   (409k ÷ 259k tokens, already in desc). Simplest, loses the at-a-glance comparison
   across the four denominators.
3. Clamp the track only (max: Math.max(100, percent)). One line, but it rescales the
   other three bars against a moving axis, which makes them incomparable between page loads.

Do not touch the arithmetic — the gross-over-attempted definition is deliberate and
documented; this is a rendering issue only.

Raised in review of #138 and deliberately left out of that PR: it is a change to the headline
savings display, affects all four denominator rows, and belongs with its own screenshot
verification rather than bolted to a components/offload fix.