fix(ui): pin the box height of single-line chips so leading cannot move them #1879

Problem

Astryx sizes a chip's box and its line box off the same 4px scale, so the two agree by construction: Badge and Kbd set height: var(--spacing-5) (20px) with display: inline-flex; align-items: center, and carry --text-supporting-leading, which is also 20px. The leading cannot move the box because the box is pinned to the value the leading already has.

Several Maka chips pin neither. They let the line box decide the height, so any leading change is a layout change. Measured live during the leading convergence (#1878) by applying the new leading in the running document and remeasuring the box:

.maka-plan-card-run is the shape the others should have: its height is fixed, so the same leading change moved nothing.

Scope

Give the single-line chip family the Astryx shape — a pinned height off the spacing scale plus inline-flex centring — so leading and box height stop being two independent decisions. Covers the former line-height: 1 sites (kbd, tags, button labels, counts, timestamps) and the 12px badges.

Coverage limit

The table is what six e2e fixture scenarios render. Chips on surfaces no fixture boots (.plan-proposal-step-number, .plan-execution-step-marker, .maka-composer-skill-trigger-count, .maka-composer-revision-notice, .settingsUsageRecordCount, .settingsUsageDetailToggle, .maka-sidebar-update-button) were not measured live and need the same check before being changed.

Context

Not folded into #1878, which was scoped to leading only: where a box grew there, it grew, and the PR says so rather than absorbing it into padding.