No Docker healthchecks: the daemon keeps /metrics' counts itself (#218)

Docker runs a healthcheck with exec, and containerd puts each exec's state in XDG_RUNTIME_DIR,
/run/user/0 on Tower, which elogind removes when root's last session ends. Every check then
failed and every container showed unhealthy while all of them answered. The checks are gone from
the sample compose file and production's; ipx's library counts for /metrics, which only the
healthcheck's status call refreshed, are counted every 30 s by the daemon.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/directory/src/main.rs

@@ -25,8 +25,7 @@ enum Cmd {
         #[command(subcommand)]
         cmd: TokenCmd,
     },
-    /// Check that the directory on this machine answers and can read its database: the
-    /// container's healthcheck.
+    /// Check that the directory on this machine answers and can read its database.
     Health,
 }