[F42] cargo doc --workspace --no-deps clean (0 warnings)

Fix all 33 rustdoc warnings across the workspace:

- Unresolved intra-doc links: rewrite [`name`] → either backtick text
  (when not actually a link) or fully-qualified `[Type::method]` /
  `[crate::module::name]` form. Affected: mxaccess-codec
  (asb_variant, item_control, metadata_query, observed_write_template,
  reference_handle, write_message), mxaccess-rpc (pdu), mxaccess-nmx
  (client), mxaccess-asb-nettcp (nmf), mxaccess-callback (exporter),
  mxaccess (asb_session, session, lib).
- Bracket-text being interpreted as link refs (e.g. `body[17]` →
  `` `body[17]` ``).
- Private-item references in public docs (CALLBACK_BROADCAST_CAPACITY,
  recover_connection_core, mxvalue_to_writevalue) reduced to
  backtick-text since they aren't part of the public API.

`RUSTDOCFLAGS="-D warnings" cargo doc --workspace --no-deps` now
exits clean. Workspace 759 tests pass; clippy clean.

Defers `#![warn(missing_docs)]` lint to a future pass — the cleanup
target is the broken-link warnings, which are signal; missing-docs
would surface hundreds of low-priority public-item gaps that are out
of scope for this F-number.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

rust/crates/mxaccess-codec/src/metadata_query.rs

@@ -1,7 +1,7 @@
 //! `NmxMetadataQueryMessage` — observed pre-advise metadata-query body.
 //!
 //! Direct port of `src/MxNativeCodec/NmxMetadataQueryMessage.cs`. The .NET
-//! reference exposes a single static helper, [`encode_observed_pre_advise`],
+//! reference exposes a single static helper, `encode_observed_pre_advise`,
 //! which returns a fixed observed body with a 16-byte item-correlation GUID
 //! patched in at offset `0x8a`.
 //!