Give the three hero columns one width, and the label back the space it lost (#1502)

[ryanbr]

Fixes #1502 — "REST" showing as "R…" under the Today hero, and the three rings not looking the same size.

One cause, both symptoms

Charge and Effort size their columns to their own label rows. Rest alone sits in a box pinned to the
ring diameter, because that box anchors the card's source badge:

// Its fixed-width box also anchors the card-level source badge:
// the badge may grow leftward, but its trailing edge always matches the Rest vessel.
Box(modifier = Modifier.width(ring)) { HeroRingColumn(domain = DomainTheme.Rest, …) }

So the three columns come out different widths — which reads as rings of different sizes, even though a
single ring value feeds all three vessels — and Rest's label has the least room of the three.

The tell is that REST is the shortest of the three words. If the labels were simply too long for the
layout, CHARGE and EFFORT would break first.

Fix

All three columns now take one shared col, derived from the same maxWidth the ring is. The badge keeps
the vessel-aligned trailing edge it exists for, by insetting exactly the slack the wider column introduces.

The label was also paying for a counterweight. #937 wanted the word centred on the ring's axis rather
than the word-plus-chevron block, and balanced the row with an invisible leading twin of the chevron —
correct, but it spends a second 14.dp slot plus its gap on nothing. Inside Rest's ring-width box that left
the text barely 50.dp on a compact screen, which is where "REST" ran out of room at a larger font scale.

Centring in a Box gets the same axis for free: the column is symmetric, so a centred word sits on the
ring's centre by construction and the chevron floats at the trailing edge instead of being counterweighted.
The word reserves 16.dp each side so it can never run under the chevron at any label length.

screen	label room before	after
360.dp	50.8.dp	68.0.dp	+34%
392.dp	61.1.dp	78.7.dp	+29%
432.dp	66.0.dp	92.0.dp	+39%

The tap target grows to the full column and stays one target. RTL still mirrors (Box alignments and the
AutoMirrored icon both flip). TalkBack loses nothing — the invisible twin was deliberately
description-less, so it never announced anything.

Android only; iOS lays its hero out separately and UI parity is feature-level.

Narrow heroes

col is (maxWidth - 2*gap)/3 but ring carries a 90.dp floor, so under ~298.dp of hero width the floor
exceeds the column and the badge inset (col - ring)/2 goes negative — and Modifier.padding throws on
a negative value. That's a small phone, a split-screen pane, or a foldable's cover display; at 288.dp the
inset is −1.7.dp. Caught on re-review, before it went anywhere.

Ring is now capped at the column width — a narrow hero shrinks its vessels with their columns instead of
spilling out of them — and the inset is clamped at zero as a second line. Checked across 240–432.dp: the
inset never goes negative, the ring never exceeds its column, and three columns plus two gaps still come to
exactly maxWidth.

Verification

Full suite — 4,173 tests, 0 failures. doc_comment_lint and i18n_audit --ci clean. No new strings.

Not visually verified. I can't run the app; the arithmetic above is the whole argument. The truncation
is font-scale dependent, so it's worth a look on a device before trusting this — and @mailingjash's display
size / font size settings would confirm the diagnosis outright.

Reported by @mailingjash.