fix: expand twitter short links like FxEmbed linkFixer

Replace display_text_range slicing with FxEmbed-style content matching:
expand mapped t.co links to their real URLs (dropping internal
x.com/i/web/status pages), then strip every leftover t.co short link
(appended media link, unmapped links).

The old code cut by display_text_range, whose index unit differs per
endpoint (UTF-16 on the syndication endpoint, code points in the
GraphQL fallback), so slicing by either unit left a partial
"https://t." caption tail on the other path. Content matching is
unit-agnostic and also keeps user-posted/quote links at the end of
the text that the trailing cut previously dropped.

crates/x-media/src/site/twitter/model.rs

@@ -9,10 +9,6 @@ pub struct SyndicationTweet {
     pub user: SyndicationUser,
     #[serde(default)]
     pub possibly_sensitive: Option<bool>,
-    /// Visible-text span; the raw `text` field has the appended media short
-    /// link after it. Indices are Unicode code points (not UTF-16 units).
-    #[serde(default, rename = "display_text_range")]
-    pub display_text_range: Option<[usize; 2]>,
     #[serde(default)]
     pub entities: SyndicationEntities,
     #[serde(default, rename = "mediaDetails")]