Migrate Svelte UX components, state, attachments, and docs

- Add the Svelte 5 `@layerstack/ui` package and migrated component suite
- Add `FormState`, `ThemeState`, and new attachment APIs
- Expand component documentation and close Svelte UX parity gaps
- Fix theme synchronization, dark variants, and client-only initialization

Author: techniq

.changeset/dark-variant-system.md

@@ -0,0 +1,23 @@
+---
+'@layerstack/tailwind': patch
+'@layerstack/ui': patch
+'@layerstack/docs': patch
+---
+
+fix: Follow `prefers-color-scheme` in the `dark:` variant, not just `<html class="dark">`.
+
+There were two disagreeing sources of truth for "is it dark". The theme palettes darken from
+`@media (prefers-color-scheme: dark)` on `:root`, which needs no JavaScript, but the `dark:` variant
+was keyed on the `dark` class, which is only ever set by JavaScript. Any moment the two disagreed —
+before hydration, or permanently when no dark themes are registered — produced dark surfaces with
+every `dark:` utility still in its light state. Most visibly, code blocks styled by
+`dark:text-(--shiki-dark)` rendered near-black tokens on a dark background.
+
+The variant now mirrors the palettes: an explicit `[data-theme]` selection wins, and everything else
+follows the system setting. `@layerstack/docs`' `Code` component gets the same treatment for its
+hand-written `html.dark .shiki` rules.
+
+Also fixes `ThemeInit` on client-only apps. It injects its pre-paint script through `{@html}`, and
+the browser never executes a `<script>` inserted that way — so with `ssr = false` the guard was
+inert. `@layerstack/tailwind` now exports `applyInitialTheme`, which `ThemeInit` calls directly in
+the browser.

.changeset/docs-parity.md

@@ -0,0 +1,18 @@
+---
+'@layerstack/docs-site': patch
+---
+
+docs: Close the concept gaps against the Svelte UX docs.
+
+Every old component page was compared against the new one and the missing concepts were added —
+around 130 new examples across ~55 components, consolidated so one example usually covers what used
+to be several sections. Notable additions: `Progress` color/track/color-by-value, `Month`,
+`MonthList`, and `YearList` selection and disabled-date shapes, `Steps` points and colors,
+`Timeline` layouts, `TextField` adornments/multiline/debounce, `SelectField` states and non-string
+option values, `MultiSelect` option variants and slots, `Drawer` placement and persistence,
+`Selection` select-all/single/max, and the `Gooey`/`Shine`/`Tilt` effect parameters.
+
+Also fixes five pre-existing type errors in `Table`, `TreeList`, `Popover`, and `Badge` examples.
+
+Examples now collapse their source by default — only the first example on a page keeps `showCode`,
+since it doubles as the "how do I use this" sample. The rest are one click away behind **Show code**.

.changeset/form-state.md

@@ -0,0 +1,13 @@
+---
+'@layerstack/svelte-state': minor
+---
+
+feat: Add `FormState` — the runes replacement for `@layerstack/svelte-stores`' `formStore`.
+
+`draft` is a deeply reactive copy that inputs bind to directly, so the `refresh()`/`current` dance
+the immer-draft-based store required is gone. `commit()` validates against an optional schema and
+promotes the draft to `state`; `revert()`, `revertAll()`, and `undo()` walk it back. `isDirty` and
+`canUndo` replace `dirtyStore`.
+
+The schema is typed structurally (anything with a zod-compatible `safeParse`), so the package
+depends on neither zod nor immer.

.changeset/layerstack-ui.md

@@ -0,0 +1,5 @@
+---
+'@layerstack/ui': minor
+---
+
+feat: Add `@layerstack/ui` package — Svelte 5 successor to `svelte-ux`, starting with `Icon`, the component settings/theme system (converted to runes), and shared types

.changeset/real-keys-battle.md

@@ -0,0 +1,5 @@
+---
+'@layerstack/svelte-attachments': minor
+---
+
+feat: Add `@layerstack/svelte-attachments` package

.changeset/svelte-attachments-overlay.md

@@ -0,0 +1,8 @@
+---
+'@layerstack/svelte-attachments': minor
+'@layerstack/svelte-table': patch
+---
+
+feat: Add `portal`, `popover`, and `scrollIntoView` attachments. `popover` takes an `onClickOutside` callback in place of the `clickOutside` custom event.
+
+`tableOrderStore().onHeaderClick` now accepts either `{ column }` or a `CustomEvent`-shaped `{ detail: { column } }`, so it works with both `@layerstack/ui`'s `Table` and Svelte UX's.

.changeset/theme-desync.md

@@ -0,0 +1,29 @@
+---
+'@layerstack/svelte-state': patch
+'@layerstack/svelte-stores': patch
+'@layerstack/tailwind': patch
+'@layerstack/docs': patch
+---
+
+fix: Stop the fallback settings from stripping the applied theme, and derive `dark:` from the themes.
+
+`getSettings()` builds a fallback outside a `settings()` provider, and that fallback constructed a
+theme store with **no themes configured**. Its constructor still ran, read `localStorage`, wrote
+`<html data-theme="dark">`, and then — because `[].includes('dark')` is false — *removed* the `dark`
+class the real instance had just applied. The result was `data-theme="dark"` with no `dark` class:
+a dark palette with every `dark:` utility still light, most visibly light code tokens on a dark
+background. Whether it happened at all depended on when the fallback was first touched, which is why
+it was intermittent, and why toggling the theme fixed it.
+
+A theme store with nothing configured is now inert — it never touches the document or
+`localStorage`. A stored theme the app no longer defines is also ignored rather than applied, since
+it cannot be classified as light or dark.
+
+The `dark:` variant is now generated from the themes themselves. A theme declares its darkness with
+`color-scheme: dark`, so that is the single source of truth: `@custom-variant dark` lists every dark
+`[data-theme]` alongside `.dark` and the `prefers-color-scheme` fallback. The palette and the variant
+can no longer disagree, whatever JavaScript does.
+
+`@layerstack/docs` moves its Shiki color rules out of `Code.svelte`'s `<style>` block — Svelte
+compiles those, so Tailwind never saw the `dark:` variant there — and into `styles.css`, which also
+covers the runtime-highlighted blocks that the markdown-only rule missed.

.changeset/theme-state.md

@@ -0,0 +1,5 @@
+---
+'@layerstack/svelte-state': patch
+---
+
+feat: Add `ThemeState` (replaces `createThemeStore` from `@layerstack/svelte-stores`) and export a `breakpoints` constant

.changeset/ui-code-copybutton.md

@@ -0,0 +1,7 @@
+---
+'@layerstack/ui': minor
+---
+
+feat: Add `Code` and `CopyButton`. `shiki` and `@shikijs/transformers` are optional peer dependencies — `Code` renders plain text when they are not installed.
+
+`ApiDocs`, `StoreSubscribe`, `State`, and `Preview` are not being migrated from Svelte UX; see `MIGRATION.md` for replacements.

.changeset/ui-form.md

@@ -0,0 +1,12 @@
+---
+'@layerstack/ui': minor
+---
+
+feat: Migrate `Form`, the last remaining Svelte UX component.
+
+- The nine slot props collapse to a single `{ form }` snippet argument — a `FormState` carrying
+  `draft`, `state`, `errors`, `isDirty`, `canUndo`, `commit`, `revert`, `revertAll`, and `undo`.
+- `on:change` is the `onChange(value)` callback prop, and no longer fires on mount.
+- `refresh()`/`current` are gone: `form.draft` is deeply reactive, so `bind:value={form.draft.name}`
+  is enough.
+- A `form` prop accepts externally owned `FormState`, for reading or driving the form from outside.