fix(fetch): one status table — a persistent 4xx is permanent everywhere

status_error's catch-all called every unlisted status Transient, so a 400/405/418/451 got three retries per link before the same answer (twitter syndication's broken-token 400 being the live example), and download_status_error plus misskey's and bilibili's local fallbacks each carried their own copy of the table — bilibili and misskey classifying a 404 as Transient while the center classified it NotFound. The center now makes any client error except 408/429 a refusal (permanent), the media path delegates to it as status_error("media", ...) and its duplicated fn is deleted, and misskey/bilibili fall through to the center after their own special statuses (misskey's 400 body, bilibili's 412). A table test pins every class.

crates/x-media/src/site/bilibili/interface.rs

@@ -213,10 +213,11 @@ pub async fn fetch(dynamic_id: &str) -> Result<model::Item, FetchError> {
     if !status.is_success() {
         return Err(match status.as_u16() {
             412 => risk_control("412"),
-            // A refusal or an auth demand is not a bad moment (412 above is
-            // bilibili's risk control, which does clear on its own).
-            401 | 403 => FetchError::Blocked,
-            _ => FetchError::Transient(format!("bilibili status {status}")),
+            // Everything else shares the central classes (refusals and gone
+            // posts permanent, 429/5xx retried). The local fallback used to
+            // disagree: a bilibili 404 came back Transient here. 412 above is
+            // bilibili's risk control, which does clear on its own.
+            _ => crate::site::status_error("bilibili", status),
         });
     }
     let detail: model::Detail = response.json().await.map_err(|e| FetchError::Site {