Suprnova v1.1.0

Added

• Per-locale fallback chains. LocalizationConfig gains parents
  (APP_LOCALE_PARENTS, comma-separated child=parent pairs, or the
  chainable .parent(child, parent) builder): a locale can inherit from a
  configured sibling before falling further back to the global
  fallback_locale — pt-PT from pt-BR, en-AU from en-GB, and so
  on, transitively. Lang::get/try_get/get_with/try_get_with/has
  all walk the chain, current locale first, so this works for any
  Translator driver, not just the bundled one. A malformed pair, an
  invalid locale, a child named twice, or a cycle (including a locale
  naming itself as its own parent) fails loudly at config load rather
  than degrading at request time.

  Served catalogs stay chain-flattened ahead of time: FluentTranslator
  now builds each locale's /_suprnova/lang/<locale>.ftl catalog as a
  fold — the embedded framework catalog at the bottom for en/en-*
  locales, then the locale's configured parent chain, then its own
  *.ftl files — so a chained locale is still one self-contained file
  the browser fetches once, with no client-side chain awareness needed.
  Flattening covers configured parents only; the terminal
  fallback_locale is still a Lang-facade-level fallback, not baked
  into the served bytes.

  This makes delta-style catalogs practical: a lang/pt-PT/ directory
  can hold only the handful of strings that actually differ from
  lang/pt-BR/, rather than a full duplicate catalog. The merge that
  makes it possible works at the Fluent AST level — a child's value
  replaces the parent's, attributes merge by name (an override that
  doesn't mention an attribute no longer loses it), select expressions
  replace whole (CLDR plural categories are locale-dependent, so
  variant-by-variant merging isn't coherent), and child-only entries
  append. See manual/localization.md's new "Fallback chains" section
  for the full contract.

Changed

• LocalizationConfig gained the parents field. from_env() and
  the builder are unaffected; a literal struct constructor (tests
  building a LocalizationConfig by hand) needs one more field.
• Served catalog text is now serializer-normalized for every locale,
  and intra-locale multi-file merging (several .ftl files in one
  locale directory) now goes through the same AST-level merge as parent
  chains rather than simple bundle-overriding. Resolved translations are
  unchanged except for the two strict improvements below; the
  underlying bytes rotate regardless — ETag/?v=<hash> rotates once
  on upgrade. The improvements: an override no longer silently drops
  the attributes it doesn't mention, and an attributes-only override no
  longer strips the message's own value (previously an error or a
  fallback resolution; it now resolves to the earlier override's
  value).