v0.5.0

Added

• Exoplanet.Filters now accepts allow_categories: :all and
  block_categories: :none to express "no constraint" explicitly.
  Lists keep working unchanged; atoms are normalized to [] internally
  by both Exoplanet.Filters.merge/2 and
  Exoplanet.Config.from_file/1, so the struct's default_filters
  field is always in canonical list form. Invalid atoms
  (allow_categories: :none, block_categories: :all, or any
  unrecognized atom) raise ArgumentError at config-load / merge time.
  The Exoplanet.Filters.t() typespec is widened accordingly.

Fixed

• Exoplanet.build/1 now sorts each feed's entries by published
  (descending) before applying the per-feed new_feed_items cap.
  Previously the first N entries in document order were kept, so feeds
  that don't list newest-first (some Bridgetown / Jekyll templates,
  podcast feeds) had genuinely recent posts dropped before the global
  merge.
• The feed parser now trims trailing , / ; and surrounding
  whitespace from feed categories at extraction time. Some Atom feeds
  emit terms like otp, (apparent producer-side templating bug) which
  silently failed Exoplanet.Filters.passes_allowlist? against the
  canonical otp allow-list entry, dropping the post.
• The Atom parser now derives Exoplanet.Post.id from the entry's
  <link rel="alternate"> (or any <link> without a rel, per
  RFC 4287 §4.2.7.2) before falling back to <id>. Bridgetown-style
  feeds emit <id>repo://posts.collection/_posts/...md</id> and the
  canonical web URL only lives in <link rel="alternate">; consumers
  were rendering the repo:// URN as a clickable link.