ATM page needs more semantic markup

The output here needs a bit more semantic markup:

• include role="main" or main element wrapping the entire main page content;
• introduce the main section with an h1 which wraps the relevant title of the page (ATM Output for xxx) or some such;
• There is an h1 which reads: "No annotations!" This is the only heading on the page. This should be demoted to h2, or perhaps lower if it is contained within another subsection.
• There is bold text which reads: "navigation" just before some toolbar buttons labeled like "<<", "<", "*", ">", ">>", etc. Use a heading tag instead of simply marking it as bold text.
• There is text which reads: "current observation window -- click on either side to move it". Mark this up as a heading.
• Within the observation window, somehow separate the various items either via list markup, heading markup, wrap each distinct item in a container like div with role="article", or use role="region" and then add a label to each via aria-label.

Locate the implementation of the ATM output page and inspect how its headings, toolbar, observation window, and page container are currently rendered. Use the issue’s semantic-markup requirements as the checklist, then verify that the page has a meaningful heading hierarchy and identifiable content regions with an accessibility inspection.