feat(design): every button on its family, the chip primitive, the lint rule (E28 S3b2)

The second half of the button sweep: the remaining hand-rolled buttons in
feature components, the design lab and the components/ui composites now
stand on Button, IconButton, Pressable, Chip or DragHandle.

- Chip + DismissibleChip (filter / token / tag / suggest / ghost, 24px
  floor, 44 on touch) replace five chip geometries; FilterChipGroup
  renders Chips; overflow lanes measure a mirror painted by chipClass.
- The Plex control row is IconButton's player rung (36, 20px glyph,
  round, overlay; 44 on touch); the YT modal bar is on the sm rung with
  pressed cycle toggles and names that survive a folded label.
- New variants: IconButton ghost-accent, danger-soft; Button warn on a
  new state-warn utility. The .btn-{tone} recipes and btnCls are gone.
- Fixed on the way: membership rows (collection editor, Plex playlist
  add) announce checked/mixed; a one-letter tag chip was 21px wide;
  descriptionLinks moved out of lib/ (it renders components).
- local/button-primitive: a raw <button>/<FocusSafeButton> outside the
  control-primitive files is a lint error (contract-tested, seen red).

CLAUDE.md

@@ -92,7 +92,7 @@ CQRS, a repository/DI framework, a router library, a generic CRUD-router factory
 | Job status word                      | the `downloads/status.py` StrEnum                                                                                       | loose `"canceled"`/`"cancelled"` literals                                            |
 | Current time                         | inline `datetime.now(timezone.utc)`                                                                                     | new `now_utc`/`_now` helpers                                                         |
 | FE per-account state                 | `usePref`                                                                                                               | raw `readAccount`/`writeAccount` or bespoke hooks                                    |
-| FE button                            | `ui/Button` (a `SIZES` rung) · `IconButton` · `Pressable` (a clickable card/row)                                        | a hand-rolled `<button className="px-3 py-2 …">`                                     |
+| FE button                            | `ui/Button` (a `SIZES` rung) · `IconButton` · `Pressable` (a clickable card/row) · `Chip` · `DragHandle`                | a raw `<button>` outside `components/ui/` (lint-enforced)                            |
 | FE keyboard shortcut                 | a row in `lib/keymap.ts` + `dispatch()`                                                                                 | a private `keydown` listener with its own key literals                               |
 | FE list/grid keys                    | `NavGrid`/`keyboardNav` + `navItemAttrs` + `data-nav-open`                                                              | a private arrow-key / roving-tabindex handler                                        |
 | FE view push (history)               | `rememberNavPosition()` right before `history.pushState`                                                                | a push that forgets: Back strands focus on `<body>`                                  |