@spec classes(boolean(), Tails.input(), Tails.input()) :: String.t()

Resolves the final class value for a component given its paperize flag.

When paperize is true, the component's Material Design classes are kept and merged with the caller-supplied class using PhoenixPaper.Tails (so conflicting Tailwind utilities are deduplicated, last one wins) — that's a Tails.Custom instance rather than plain Tails, so it recognizes our pp-* color tokens; see its moduledoc for why that distinction matters.

When paperize is false, the component's built-in classes are dropped entirely — only the caller-supplied class is rendered, giving the caller a bare, unstyled element to skin with their own CSS.

@spec toggle_label_classes(Tails.input()) :: String.t()

The classes for a toggle control's wrapping <label> — Checkbox, Switch, and each of RadioGroup's per-option labels all need the same inline-flex items-center gap-2 to arrange their box/track next to the label text.

Unlike classes/3, this is not gated behind paperize — it's always merged in via PhoenixPaper.Tails, extra_class and all. This layout isn't part of the "paper" skin paperize={false} is meant to strip (compare paperize's own doc: colors/elevation/shape/typography); it's the structural arrangement of the label itself, and there's no other class attr on that specific label for a caller to rebuild it with — same reasoning as AppBar's inner toolbar <div> and Breadcrumbs's <li>s (see AGENTS.md, "The paperize contract"). Dropping it doesn't give paperize={false} a cleaner slate, it just breaks the box-plus-text layout with no way back — found from a real screenshot of Checkbox's paperize={false} demo where the caller's own class="size-5" (meant to size the bare <input>, since that's the one truly skinnable element left when paperize={false}) landed on this label instead and shrank the whole row to nothing. Checkbox/Switch fixed the targeting half of that bug by routing class to the bare input instead of this label when paperize={false}; this function fixes the layout half so the label never collapses either way.

@spec translate_error({String.t(), keyword()}) :: String.t()

Interpolates a Phoenix.HTML.FormField error tuple's %{key} placeholders (e.g. {"must be %{count} characters", [count: 3]}), without depending on Gettext. Shared by every form component (Input, Select, NumberField, ...) that accepts field= and renders field.errors.