style(storybook): unify content hierarchy and section spacing

- Story page frame: H2 16/24/700 -> 12px -> divider -> 16px -> content, sections 28px apart;
  StorySectionGrid keeps its 24px column gap
- Content indent (--sb-page-indent 16px, 12px at 640px and below): .sb-page-indent for information
  blocks; group boards (StateBoard / CardBoard, data-sb-board) indented once per section block so
  per-column boards keep their 24px gap
- Input / Select / Toggle Sizes grids take the same indent; field Labels unchanged
- Full-width Pattern previews (GNB, LNB, Loading Screen, Page Header) opt out with indent={false}
- Foundation/폰트: Text Colors name / usage / HEX levels, Font Family and Font Weight token lines,
  Specimens row spacing and indent; specimen values unchanged
- Guideline and WORKING_CONTEXT updated

src/components/input.stories.tsx

@@ -134,7 +134,10 @@ export const All: Story = {
     <StoryPage>
       <StoryPageHeader title="Input" />
       <StorySection title="Sizes">
-        <SizeComparison showSpec={false} />
+        {/* Same common indent as the group boards below; Small / Medium / Large stay the fields' own Labels. */}
+        <div className="sb-page-indent">
+          <SizeComparison showSpec={false} />
+        </div>
       </StorySection>
       <StorySection title="States">
         <StateBoard