docs: use per-comment reference defs for field links (tidy-compatible)

rust-llm-tidy's link op collapses inline [x](Self::x) links into
reference-style [x] + [x]: Self::x. That breaks rustdoc: reference
definitions are scoped to the single doc comment they appear in, so defs
on one field's docs cannot serve uses on neighboring fields' docs. The
op also appends the defs at EOF outside any comment, yielding invalid
Rust.

Variant C keeps the reference style tidy prefers, but duplicates each def
inside every doc comment that uses it, so each comment is self-contained:
rustdoc stays green (-D warnings) and rust-llm-tidy leaves the file alone
(dry-run reports no changes).

Author: Sewer56

src/reloaded-code-bubblewrap/src/profile/builder.rs

@@ -106,11 +106,18 @@ pub struct Builder {
     pub(crate) read_only_host_rootfs: bool,
     /// Controls whether the sandbox has network access.
     pub(crate) network_policy: NetworkPolicy,
-    /// When `true`, inherited env vars are cleared before applying [`default_env`](Self::default_env) and [`extra_env`](Self::extra_env).
+    /// When `true`, inherited env vars are cleared before applying [`default_env`] and [`extra_env`].
+    ///
+    /// [`default_env`]: Self::default_env
+    /// [`extra_env`]: Self::extra_env
     pub(crate) clear_env: bool,
-    /// Env vars always set (applied before [`extra_env`](Self::extra_env)).
+    /// Env vars always set (applied before [`extra_env`]).
+    ///
+    /// [`extra_env`]: Self::extra_env
     pub(crate) default_env: Arc<[EnvVar]>,
-    /// Additional env vars set on top of [`default_env`](Self::default_env).
+    /// Additional env vars set on top of [`default_env`].
+    ///
+    /// [`default_env`]: Self::default_env
     pub(crate) extra_env: Arc<[EnvVar]>,
     /// Tracks whether `bwrap` is usable (checked during [`build`](Self::build)).
     pub(crate) availability: Availability,