docs+comments: say what changed instead of tagging the tracker item

The prose added by this branch named the tracker item in seventeen
places, which check-issue-refs.sh rejects: a `#N` tag is dead weight for
anyone reading the public mirror, where no issue data exists. Each one
now states the fact it was pointing at — the parent field is gone — so
the sentence stands on its own.

Two of those lines also carried a rustdoc break: `[`write`]` in
topology.rs is ambiguous between the module's own `write` fn and the
`write!` macro, which `-D rustdoc::broken-intra-doc-links` fails. Spelled
`[`write()`]`, per rustdoc's own suggestion.

The host_config.rs rewrite is two lines rather than three so the doc
block stays under check-comment-blocks.sh's 30-line ceiling.

hive-c0re/src/agent_config/topology.rs

@@ -6,7 +6,7 @@
 //! **There is no hierarchy here any more.** The file used to be a map of
 //! `name → parent | null` and this module owned the parent/child tree that
 //! fed `<parent>` / `<children>` routing, the reparenting API and the
-//! dashboard's tree view. All of that is gone (#4472); what the file is
+//! dashboard's tree view. All of that is gone; what the file is
 //! *for* now is the one thing that survived the removal — naming every
 //! agent, which is the set a
 //! [`hive_sh4re::permissions::Capability::ManageRootAgent`] holder gets
@@ -28,8 +28,8 @@ pub fn topology_path() -> PathBuf {
     crate::paths::meta_root().join(TOPOLOGY_FILE)
 }
 
-/// On-disk shapes [`read`] accepts. The array is what [`write`] emits; the
-/// map is the pre-#4472 `name → parent | null` format, kept readable so a
+/// On-disk shapes [`read`] accepts. The array is what [`write()`] emits; the
+/// map is the legacy `name → parent | null` format, kept readable so a
 /// hive that upgrades across this change keeps its roster instead of
 /// blanking it until the next `reconcile` pass — and a blank roster is not
 /// a cosmetic gap, it is every `ManageRootAgent` holder losing its mounts
@@ -204,7 +204,7 @@ mod tests {
     }
 
     /// The upgrade path. A hive whose `topology.json` still carries the
-    /// pre-#4472 `name → parent` map must read as the same roster, parent
+    /// legacy `name → parent` map must read as the same roster, parent
     /// values discarded — otherwise the first read after the upgrade hands
     /// `ManageRootAgent` holders an empty mount set.
     #[test]

hive-c0re/src/job_queue/exec.rs

@@ -862,8 +862,8 @@ async fn run_deploy_tail(
 /// flake affects — the fan-out set for `MetaUpdate` DAGs. Empty
 /// `inputs` or any input under `hyperhive` → every container;
 /// otherwise just the agents named by `agent-<name>` inputs.
-/// Sorted by name — #4472 removed the parent field the old depth sort
-/// keyed on, and with every agent a root that sort already reduced to
+/// Sorted by name — the parent field the old depth sort keyed on is
+/// gone, and with every agent a root that sort already reduced to
 /// this.
 ///
 /// `inputs` is the caller-supplied flake-input-name list (the dashboard's

hive-c0re/src/lifecycle/host_config.rs

@@ -92,8 +92,8 @@ fn config_bind_source(name: &str) -> PathBuf {
 /// directories so nspawn doesn't refuse to start; missing dirs are
 /// non-fatal.
 ///
-/// The only caller left is the `ManageRootAgent` grant — #4472 removed the
-/// parent/child tree that used to hand every agent its own children here.
+/// The only caller left is the `ManageRootAgent` grant; the parent/child
+/// tree that handed every agent its own children here is gone.
 ///
 /// **Three dirs, three different answers** — the uniformity of the
 /// original loop is what hid that:
@@ -335,8 +335,8 @@ async fn set_nspawn_flags(
     // now says so out loud instead of deriving it from a field that no
     // longer discriminates.
     //
-    // This is the *only* cross-agent mount left. #4472 dropped the
-    // topology parent field, and with it the unconditional grant every
+    // This is the *only* cross-agent mount left. Dropping the topology
+    // parent field took with it the unconditional grant every
     // agent used to get over its own direct children — so an agent with
     // no capability now sees its own dirs and nothing else.
     if crate::capabilities::has_cap(agent_name, Capability::ManageRootAgent) {

hive-c0re/src/workers/auto_update.rs

@@ -267,8 +267,8 @@ pub async fn run(coord: Arc<Coordinator>) -> Result<()> {
 
     let current_rev = current_flake_rev(&coord.hyperhive_flake);
 
-    // Resolve container names to logical agent names, then sort. #4472
-    // removed the parent field this used to depth-sort by; with no
+    // Resolve container names to logical agent names, then sort. The
+    // parent field this used to depth-sort by is gone; with no
     // hierarchy left to respect, alphabetical is the whole order — and it
     // is exactly what the depth sort already produced once every agent
     // was a root.