Both cards showed their actions as two rows of TEXT buttons — a
Parent/Child navigation row above a Cancel/Add note footer — because four
labelled buttons do not fit across the card's 260pt. Four 28pt Lucide
glyphs do, so the split row was a symptom of the labels rather than of
the grouping.

- Four glyphs added to `LucideIcon` from lucide.dev's current `d`
  strings: `arrow-up`, `arrow-down`, `undo-2`, `send`. `undo-2` ships as
  two chained 5.5-radius quarter arcs, which only render as a loop
  because of the arc support added earlier in this epic; `LucideArcTests`
  now pins the SHIPPED glyph's 45-degree points, since a flattened arc
  keeps its endpoints and would pass every other check.
- `PillButton` becomes `IconButton`, parameterised by an
  `IconButtonPalette`. One implementation of the interaction logic (hover
  wash, disabled dim, press scale, tooltip + matching accessibility
  label) now serves the dark pill and the `.regularMaterial` cards; the
  pill's palette reproduces its previous colours exactly, so its
  appearance is unchanged.
- Composer: [arrow-up] [arrow-down] … [undo-2] [send]. Editor: [trash] …
  [send]. Icon-only, each with the full label in both a tooltip and an
  `accessibilityLabel`. The commit action keeps its prominence through an
  accent tint now that `.borderedProminent` is gone. Every disabled rule,
  the destructive treatment, the `⏎ save · ⇧⏎ newline` hint, and the
  session-driven draft clearing are unchanged.
- `AnnotationCard` loses its `navigation` slot: it existed only to hold
  the second row.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>