docs(websocket,gateway): fix rustdoc link warnings, restore -D warnings doc gate

- dispatch.rs: qualify [invoke]/[invoke_streaming] as
  [GatewayDispatch::invoke]/[::invoke_streaming] (module-level docs
  need the type-qualified path)
- byte_adapter.rs: drop redundant explicit link targets for
  DEFAULT_WS_WRITE_TIMEOUT / DEFAULT_WS_IDLE_TIMEOUT (already
  re-exported at crate::websocket)
- from_wss.rs, byte_adapter.rs: backtick WssSession::drop and the
  private WsFraming (all-features-only link errors, same class)
- Ws pump/timeout module docs spot-checked against WS-13/18/17 impls:
  no drift found

RUSTDOCFLAGS="-D warnings" cargo doc --no-deps now exits clean both
default-features and --all-features.

docs(tasks): mark review-002-fu-doc-warnings done

tasks/infra/review-002-fu-doc-warnings.md

@@ -1,7 +1,7 @@
 ---
 id: review-002-fu-doc-warnings
 name: Fix cargo-doc warnings (dispatch intra-doc links, byte_adapter redundant link) — restore the -D warnings doc gate
-status: pending
+status: done
 depends_on: []
 scope: single
 risk: low