swarm-queue-client: fully-qualify the wanted-module doc link to bucket

`docs-rustdoc` fails on the `//!` header: `unresolved link to bucket`,
for an item declared in that very module. The module's docs are merged
from two fragments — the `///` on `pub mod wanted;` in `lib.rs` and the
`//!` inside the file — and the merged doc does not resolve a bare item
name against the module. Every other link in the file was already
fully-qualified (`crate::status`, `crate::status::BUCKET`), so this one
was the outlier rather than the convention.

Evidence, same command before and after: `cargo doc -p swarm-queue-client
--no-deps --document-private-items` went from 1 occurrence of the error to
0, while the unrelated diagnostic in that narrower build stayed at 1 —
the surviving one is the control that the lint is still armed. The
CI-shaped run (`--workspace`, which is what unifies features) exits 0 and
documents 27 crates including this one.

Refs #4006.

swarm-queue-client/src/wanted.rs

@@ -1,6 +1,7 @@
 //! The hive-wanted KV buckets: the agent set the controller declares for each
-//! hive, **one bucket per hive** (see [`bucket`] for why the split is a grant
-//! boundary rather than a data-modelling choice), keyed inside it by `hiveName`.
+//! hive, **one bucket per hive** (see [`crate::wanted::bucket`] for why the
+//! split is a grant boundary rather than a data-modelling choice), keyed inside
+//! it by `hiveName`.
 //!
 //! Sibling of [`crate::status`] and deliberately **not** a mirror of it: that
 //! one is **observed** — each hive republishes what it is, so its store losing