feat(floating): cascade the canonical gap to all menus + panels

Stamp `data-floating-gap` on every floating content so the token-driven offset
(the foundation from the previous commit) drives the whole set, replacing the
hardcoded per-component sideOffsets (0/4/6/8):
- menus (dropdown, context, their sub-menus, menubar, select, navigation-menu) =
  flush (`menu`, gap 0);
- panels (combobox, link-preview, popover, and the 5 pickers via composed
  PopoverContent) = `panel` (gap --space-1-5).

The stamp is CONDITIONAL (`sideOffset === undefined ? archetype : undefined`,
matching split-button): a consumer-set `sideOffset` still wins (the Popover /
picker demos document `sideOffset={N}`); only the default falls through to the
canonical token. The pickers default their `sideOffset` to undefined so they
follow the panel token instead of a hardcoded 6.

Verified in-browser: navigation-menu (demo sets no sideOffset) stamps
`data-floating-gap="menu"` (STAMP branch); combobox / date-picker / dropdown
(demos set sideOffset) stamp nothing (SUPPRESS branch -- override respected). The
token-driven offset itself was validated in the pilot commit. check 0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/uix/eidos/components/color-picker/color-picker-content.svelte

@@ -8,7 +8,7 @@
 	let {
 		size,
 		align = 'start',
-		sideOffset = 6,
+		sideOffset,
 		collisionPadding = 12,
 		children: bodyContent,
 		...rest

src/uix/eidos/components/combobox/combobox-content.svelte

@@ -40,6 +40,7 @@
 	style={composedStyle}
 	data-list-surface=""
 	data-depth="overlay"
+	data-floating-gap={rest.sideOffset === undefined ? 'panel' : undefined}
 	data-size={resolvedSize}
 	data-variant={resolvedVariant}
 	data-color={resolvedColor}

src/uix/eidos/components/context-menu/context-menu-content.svelte

@@ -22,7 +22,7 @@
 	setListSurfaceSizeContext({ getSize: () => resolvedSize });
 </script>
 
-<ContextMenu.Content data-stagger="" data-list-surface="" data-depth="overlay" {...rest} data-size={resolvedSize}>
+<ContextMenu.Content data-stagger="" data-list-surface="" data-depth="overlay" data-floating-gap={rest.sideOffset === undefined ? 'menu' : undefined} {...rest} data-size={resolvedSize}>
 	{#snippet children(snippetProps)}
 		{@render bodyContent?.(snippetProps)}
 	{/snippet}

src/uix/eidos/components/context-menu/context-menu-sub-content.svelte

@@ -20,7 +20,7 @@
 	const resolvedSize = $derived(eidos.resolve(size ?? sizeCtx?.getSize(), 'md'));
 </script>
 
-<ContextMenu.SubContent data-stagger="" data-list-surface="" data-depth="overlay" {...rest} data-size={resolvedSize}>
+<ContextMenu.SubContent data-stagger="" data-list-surface="" data-depth="overlay" data-floating-gap={rest.sideOffset === undefined ? 'menu' : undefined} {...rest} data-size={resolvedSize}>
 	{#snippet children(snippetProps)}
 		{@render bodyContent?.(snippetProps)}
 	{/snippet}

src/uix/eidos/components/date-picker/date-picker-content.svelte

@@ -9,7 +9,7 @@
 	let {
 		size,
 		align = 'end',
-		sideOffset = 6,
+		sideOffset,
 		collisionPadding = 12,
 		width,
 		minWidth,

src/uix/eidos/components/date-range-picker/date-range-picker-content.svelte

@@ -9,7 +9,7 @@
 	let {
 		size,
 		align = 'end',
-		sideOffset = 6,
+		sideOffset,
 		collisionPadding = 12,
 		width,
 		minWidth,

src/uix/eidos/components/dropdown-menu/dropdown-menu-content.svelte

@@ -34,7 +34,7 @@
 	setListSurfaceSizeContext({ getSize: () => resolvedSize });
 </script>
 
-<DropdownMenu.Content data-stagger="" data-list-surface="" data-depth="overlay" {...rest} data-size={resolvedSize}>
+<DropdownMenu.Content data-stagger="" data-list-surface="" data-depth="overlay" data-floating-gap={rest.sideOffset === undefined ? 'menu' : undefined} {...rest} data-size={resolvedSize}>
 	{#snippet children(snippetProps)}
 		{@render bodyContent?.(snippetProps)}
 	{/snippet}

src/uix/eidos/components/dropdown-menu/dropdown-menu-sub-content.svelte

@@ -21,7 +21,7 @@
 	const resolvedSize = $derived(eidos.resolve(size ?? sizeCtx?.getSize(), 'md'));
 </script>
 
-<DropdownMenu.SubContent data-stagger="" data-list-surface="" data-depth="overlay" {...rest} data-size={resolvedSize}>
+<DropdownMenu.SubContent data-stagger="" data-list-surface="" data-depth="overlay" data-floating-gap={rest.sideOffset === undefined ? 'menu' : undefined} {...rest} data-size={resolvedSize}>
 	{#snippet children(snippetProps)}
 		{@render bodyContent?.(snippetProps)}
 	{/snippet}

src/uix/eidos/components/link-preview/link-preview-content.svelte

@@ -22,7 +22,7 @@
 	const resolvedSize = $derived(eidos.resolve(size, 'md'));
 </script>
 
-<LinkPreview.Content data-depth="overlay" {...rest} data-size={resolvedSize}>
+<LinkPreview.Content data-depth="overlay" data-floating-gap={rest.sideOffset === undefined ? 'panel' : undefined} {...rest} data-size={resolvedSize}>
 	{#snippet children(snippetProps)}
 		{@render bodyContent?.(snippetProps)}
 	{/snippet}

src/uix/eidos/components/menubar/menubar-content.svelte

@@ -30,7 +30,7 @@
 	`DropdownMenu.Item` `data-animation-style="fade"` (re-used as Menubar.Item)
 	already apply — this marker is all that's needed. See dropdown-menu README → Motion.
 -->
-<Menubar.Content {...passthrough} data-stagger="" data-list-surface="" data-depth="overlay" data-size={resolvedSize}>
+<Menubar.Content {...passthrough} data-stagger="" data-list-surface="" data-depth="overlay" data-floating-gap={passthrough.sideOffset === undefined ? 'menu' : undefined} data-size={resolvedSize}>
 	{#snippet children(snippetProps)}
 		{@render bodyContent?.(snippetProps)}
 	{/snippet}

src/uix/eidos/components/navigation-menu/navigation-menu-content.svelte

@@ -4,4 +4,4 @@
 	let { children, ...rest }: NavigationMenuContentProps = $props();
 </script>
 
-<NavigationMenu.Content data-depth="overlay" {...rest}>{@render children?.()}</NavigationMenu.Content>
+<NavigationMenu.Content data-depth="overlay" data-floating-gap={rest.sideOffset === undefined ? 'menu' : undefined} {...rest}>{@render children?.()}</NavigationMenu.Content>

src/uix/eidos/components/popover/popover-content.svelte

@@ -74,7 +74,7 @@
 	style={composedStyle}
 	data-size={resolvedSize}
 	data-depth="overlay"
-	data-floating-gap="panel"
+	data-floating-gap={rest.sideOffset === undefined ? 'panel' : undefined}
 	data-animation-style={motion === 'none' ? undefined : motion}
 >
 	{#snippet children(snippetProps)}

src/uix/eidos/components/select/select-content.svelte

@@ -35,6 +35,7 @@
 	style={composedStyle}
 	data-list-surface=""
 	data-depth="overlay"
+	data-floating-gap={rest.sideOffset === undefined ? 'menu' : undefined}
 	data-size={resolvedSize}
 	data-variant={resolvedVariant}
 	data-color={resolvedColor}

src/uix/eidos/components/time-picker/time-picker-content.svelte

@@ -9,7 +9,7 @@
 	let {
 		size,
 		align = 'end',
-		sideOffset = 6,
+		sideOffset,
 		collisionPadding = 12,
 		width,
 		minWidth,

src/uix/eidos/components/time-range-picker/time-range-picker-content.svelte

@@ -9,7 +9,7 @@
 	let {
 		size,
 		align = 'end',
-		sideOffset = 6,
+		sideOffset,
 		collisionPadding = 12,
 		width,
 		minWidth,