fix(ui): the platform layer speaks platform words; boxes scale with the text

- PriorityStepper labelled itself with channels.row.* and told every caller
  it orders the Feed; Combobox said plex.loading / plex.filter.moreRefine /
  sidebar.match on the feed sidebar. The generic strings moved to common.*,
  and what a priority MEANS arrives as the stepper's `hint` prop.
  uiI18n.contract.test.ts pins components/ui/ to the platform namespaces —
  the import boundary could never see an i18n key.
- 32 px-frozen box utilities (w-[150px], max-w-[1600px], left-[18px], …)
  became spacing-scale steps (w-37.5, max-w-400, left-4.5): identical at the
  default text size, and now they grow with the Settings slider instead of
  clipping or re-wrapping their own labels. An eslint rule refuses the px
  form beside the older text-[Npx] one, pinned by pxBox.contract.test.ts;
  measured in the browser that every new step is generated at its old px.
- chipLane's import-strip regex ran past a side-effect import into the next
  statement's `from`, hiding a lane between them; it now stops at the
  import's own `;`.

frontend/src/components/ui/README.md

@@ -21,7 +21,10 @@ A component belongs here **iff its props and imports name no domain concept**. I
 It may **not** import a feature component (`../Feed`) or a domain API slice (`lib/api/*`). This is
 enforced by `no-restricted-imports` in `eslint.config.js` — not by this README, which is only the
 explanation. If a primitive needs domain data, take it as a prop or a render-prop and let the module
-supply it.
+supply it. The same goes for its words: a primitive translates only from the platform i18n
+namespaces (`common`, `errors`, `datatable`, `keys`, `palette`, `sidebar`, `notifications`, `time` —
+`uiI18n.contract.test.ts`); what a value means where it is used arrives as a prop (`PriorityStepper`'s
+`hint`).
 
 The direction is one-way from below, too: `lib/` may not import from `components/` — this directory
 included, not even a type (same lint file). A contract both layers need lives in `lib/`: the `Column`
@@ -54,10 +57,9 @@ somewhere:
   on the root font-size) scales boxes and padding with the label. A `text-[Npx]` font size is an
   eslint error for exactly this reason. The deliberate exceptions are the layout-engine measurements
   — `VirtualGrid`'s `minCol` / `colMaxWidth` and `gridColumns`' `GRID_GAP` — which are compared
-  against a container's own pixel width rather than sized against text. Two px box values are NOT
-  deliberate and are worth converting when touched: `Tooltip`'s `max-w-[240px]` (it does not widen
-  with the slider while its text does, so the tooltip re-wraps at large text sizes) and `form.tsx`'s
-  `left-[18px]` toggle knob.
+  against a container's own pixel width rather than sized against text. A px-frozen BOX utility
+  (`w-[Npx]`, `max-w-[Npx]`, …) is an eslint error too, since the 2026-09 sweep: use the spacing
+  scale (`w-37.5` is 150px at the default size and grows with the slider).
 - **Minimum target: 2.75rem, on coarse pointers only** (`.touch-target`, index.css). A 32px icon
   button is fine with a mouse and not with a thumb, so the box grows where there is no precise
   pointer. It grows the real box rather than painting an invisible hit area: two expanded hit areas