refactor(storybook): hide page headers and preserve accessibility

StoryPageHeader no longer shows the page title, kicker, description or the SW group notice; it renders only a visually hidden H1 with the Story title, so the preview keeps a page heading for screen readers while the first section starts at the top gutter (unchanged position).

- OrgChart verify-p8 / p9 / p9-1 / p9-2-composition wait for the first visible StoryPage content block and read the page H1 instead of .sb-page-title; existing expectations are unchanged.
- SW overview browser test clicks the page gutter as its outside-click target.
- Drop the unused .sb-page-description from the SW Storybook hide rules.
- Update the Storybook page frame rule in the project guideline.

examples/org-chart/verify-p9-2-composition.mjs

@@ -33,7 +33,8 @@ async function settle() {
 async function open(size) {
   await page.setViewportSize(size);
   await page.goto(`${origin}/iframe.html?id=orgchart--full-composition&viewMode=story`);
-  await page.locator('.sb-page-title').waitFor();
+  // The page title is a visually hidden H1 (2026-11-11): wait for the first visible StoryPage content block instead.
+  await page.locator('.sb-page-inner > :not(h1)').first().waitFor();
   await page.waitForFunction(() => {
     const shadow = document.querySelector('.hm-orgchart-host')?.shadowRoot;
     return shadow?.querySelector('.hm-orgchart-stage[data-workdesk-artwork]') && !shadow.querySelector('[aria-busy="true"]') && [...shadow.querySelectorAll('link[rel="stylesheet"]')].every(link => link.sheet);