fix: resolve clippy warnings

Reduce clippy warnings from54 to16 by fixing mechanical issues:

- collapsible_if: collapse nested if-let chains with let-chains
- clone_on_copy: remove unnecessary .clone() on Copy types
- manual_clamp: replace .max().min() with .clamp()
- unnecessary_cast: remove redundant type casts
- collapsible_else_if: flatten else-if chains
- contains_vs_iter_any: replace .iter().any() with .contains()
- unnecessary_closure: replace .or_else(|| x) with .or(x)
- useless_conversion: remove redundant .into() calls
- is_none_or: replace .map_or(true, ...) with .is_none_or(...)
- while_let_loop: convert loop with if-let-break to while-let

Remaining16 warnings are design-level issues (too_many_arguments,
await_holding_lock, type_complexity, new_ret_no_self) that require
architectural changes to fix.

src/tls_front/fetcher.rs

@@ -384,7 +384,7 @@ async fn fetch_via_raw_tls(
     for _ in 0..4 {
         match timeout(connect_timeout, read_tls_record(&mut stream)).await {
             Ok(Ok(rec)) => records.push(rec),
-            Ok(Err(e)) => return Err(e.into()),
+            Ok(Err(e)) => return Err(e),
             Err(_) => break,
         }
         if records.len() >= 3 && records.iter().any(|(t, _)| *t == TLS_RECORD_APPLICATION) {