Removes genuinely dead code (unused import, no-op cast, an unused
PendingGrab accessor, and TmdbClient's TV-search methods now that TVDB
fully covers that path), tightens len()>0 checks to is_empty(), swaps
two fixed-size test vec!s for arrays, restructures a match to avoid an
unnecessary unwrap_err, fixes doc-comment list indentation, and hoists
a locked-connection call out of a match scrutinee. Struct fields/enum
variants that are still meaningful but not read by current callers
(TorrentInfo::save_path, GrabCycleStats::items_seen, X1337 fallback
route, BacklogCandidate::path) get #[allow(dead_code)] rather than
deletion, same for the two 8-argument functions (too_many_arguments).
