hive-sh4re: split inbox, container, journal, and schedule wire shapes into their own modules

Closes the #3110 split — lib.rs is now just the crate doc comment and
the pub mod list.

journal.rs's new doc comment fixes a pre-existing bug: the old
JournalPriority doc text in lib.rs was actually half Capability's doc
(a leftover from an earlier reorder that moved the code but not the
comment above it).

hivectl/src/agents.rs

@@ -147,7 +147,7 @@ pub(crate) async fn agents_list(socket: &Path, json: bool) -> Result<()> {
     }
     // STATUS collapses the health flags into one space-separated token so
     // the common case (`running`) stays short and anomalies stand out.
-    let status_of = |r: &hive_sh4re::AgentStatusRow| -> String {
+    let status_of = |r: &hive_sh4re::container::AgentStatusRow| -> String {
         let mut s = if r.running { "running" } else { "stopped" }.to_owned();
         if r.paused {
             s.push_str(" paused");