Demote tab-widget body from <main> to <div>

The tab widget previously created <main> elements for both its outer
body container and per-tab content body. Combined with the shell's
own <main>, that meant every tabbed pane view had two or more <main>
landmarks per page.

The page-level <main> landmark now lives on the shell's `.app-view`
in mashlib (see SolidOS/mashlib PR). Tab widget internals become
plain <div>s so we have exactly one <main> per page.

No styling change: the widget uses `style.tabsMainElement` and
`bodyMainStyle` inline, not a `main` selector.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people

src/tabs.ts

@@ -187,7 +187,7 @@ export function tabWidget (options: TabWidgetOptions) {
   const navElement = rootElement.appendChild(dom.createElement('nav'))
   navElement.setAttribute('style', style.tabsNavElement)
 
-  const mainElement = rootElement.appendChild(dom.createElement('main'))
+  const mainElement = rootElement.appendChild(dom.createElement('div'))
 
   mainElement.setAttribute('style', style.tabsMainElement) // override tabbedtab.css
   const tabContainer = navElement.appendChild(dom.createElement('ul'))
@@ -333,7 +333,7 @@ export function tabWidget (options: TabWidgetOptions) {
     function getOrCreateContainerElement (ele: TabElement): ContainerElement {
       const bodyMain = ele.bodyTR?.children[0] as ContainerElement
       if (bodyMain) return bodyMain
-      const newBodyMain = ele.bodyTR!.appendChild(dom.createElement('main'))
+      const newBodyMain = ele.bodyTR!.appendChild(dom.createElement('div'))
       newBodyMain.setAttribute('style', bodyMainStyle)
       return newBodyMain
     }