feat(supported-languages): tick-grid table with split filters

Rewrites the interactive language table around three explicit column
groups: by resource (single-select), by customization (multi-select),
and by feature. The cells use voice-style ticks (✓, ⎋, β, —) instead
of badges; the column headers are the resource / customization /
feature names themselves.

Filter behaviour

- Resource is single-select (one product at a time); customization is
  multi-select; feature is multi-select.
- Customization availability for the active resource is derived from
  the inlined RESOURCES (the resource must list the customization as a
  feature key, e.g. voice has `glossary` and `spoken_terms`).
  `translation_memory` has an explicit override of `translate_text`
  until the API exposes TM as a /v3/languages resource. Picking an
  incompatible customization is auto-cleared.
- Feature filters are enabled only when a resource is selected and the
  resource lists that feature. For voice, `transcription` is forced on
  and the checkbox is locked.
- Two row-mask toggles ("hide beta", "hide external") render the
  affected ticks as `—` instead of dropping rows. Combining a feature
  filter with one of these toggles does exclude rows whose tick would
  be masked, so checking transcription with hide-external on filters
  out langs whose transcription is only external.
- "Clear all" sits next to the "Filters" label so the hide toggles
  stay anchored to the right edge.

Column behaviour

- Resource columns hide when only a customization is selected.
- Customization columns shrink to selected ones; if none are selected
  and a resource is, incompatible customizations also hide.
- Feature columns appear only when a resource is selected, ordered
  Auto-detection, Transcription, Tag handling, Translated speech,
  Formality, Tone, Writing style.

Other

- Footer legend documents the tick symbols + β marker.
- `beta` chip moved off the language name onto the resource / feature
  ticks (✓β / ⎋β).
- `glossary` and `style_rules` removed from the feature options; the
  customization columns cover them.
- supported-languages.mdx drops the now-redundant "Style rules are
  supported for the following target languages" paragraph — the table
  itself answers the same question.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Daniel Jones

docs/getting-started/supported-languages.mdx

@@ -18,8 +18,3 @@ The DeepL API supports the following languages. These can also be retrieved prog
   Currently, characters translated into beta languages are not billed. See [Alpha and beta features](/docs/resources/alpha-and-beta-features) for more information.
 </Info>
 
-Style rules are supported for the following target languages:
-
-<SupportedLanguages resource="translate_text" feature="style_rules" direction="target" />
-
-For more details, see the [Style Rules API documentation](/api-reference/style-rules). Writing style and tone availability for `/write/rephrase` can also be retrieved via [`GET /v3/languages?resource=write`](/api-reference/languages/retrieve-supported-languages-by-resource).