v0.5.1

Changed

• Polish the interactive viewer footer by using a unified transient-message
  model, styling warnings separately from errors, preserving fallback notices
  while search prompts are open, and simplifying the selection-mode footer.
• Make search matches easier to see in dark terminals by using a stronger
  muted background for inactive matches and reserving underline for the current
  focused match.
• Treat Esc after a completed search as leaving search mode: clear the query,
  match highlights, match count, and search footer before a later Esc quits.