Brings archive-cli to the same shape as the tamnd/* CLI family.

Changes:

• Badge row: CI, Release, Go Reference, Go Report Card, License.
• Nav links before the GIF: Install, Commands, Usage, Credentials.
• Demo GIF (docs/static/demo.gif, 524 KB): rendered from
  docs/demo/archive.tape with ascii-gif. Three interactions:
  archive search 'collection:nasa mediatype:movies' -n 5 --fields identifier,title,downloads
  (table), archive item nasa -o table (key-value summary), and
  archive wayback available https://google.com -o table (Wayback check).
• Commands table listing all 19 commands with one-line descriptions
  (replaces the bullet list).
• Usage section with representative examples, the cursor-export recipe,
  and a jq pipeline.
• Global flags block listing all persistent flags in one place.
• Credentials section kept and expanded (resolve order clarified).
• Exit codes block (0/1/2/3/4/5 with descriptions).
• Development section: directory map and make targets.
• Releasing section: annotated tag and push.
• Removed "Why", "Quick start", "What you can do with it", and "Output
  formats" sections; their content is folded into the new structure.

Also set the GitHub repo description and topics via gh repo edit.