grant manage_root_agent by stored permission only, not by the name ruth

Permission::default_for and hive-sh4re's MANAGER_AGENT are gone: every
agent with no permissions key holds Permission::DEFAULT, ruth included.
The agent-name parameters that only fed default_for go with it
(permissions::effective, HiveCopy::before_read/after_read and their
callers).

swarm-controller seeds the grant ruth held by name: at start, a declared
ruth whose permissions are unset gets DEFAULT plus manage_root_agent
written into her key, once, logged. A set key is never touched. It is a
one-shot to delete once every swarm has passed it.

The swarm UI setup assistant opens the create form with
manage_root_agent checked, so a new ruth is created with the grant.
permissions_import no longer adds ruth to the import or splits her
default. Docs and help text no longer say ruth holds the grant by
default; swarmctl-cli.md regenerated.

hive-subagent-mcp/src/swarm_models.rs

@@ -45,8 +45,7 @@ pub fn permissions_now() -> Vec<Permission> {
         .read()
         .unwrap_or_else(std::sync::PoisonError::into_inner)
         .clone();
-    let agent = std::env::var(crate::swarm_term::ENV_AGENT_NAME).unwrap_or_default();
-    last.unwrap_or_else(|| HiveCopy::read_at(Path::new(HIVE_COPY_PATH)).before_read(&agent))
+    last.unwrap_or_else(|| HiveCopy::read_at(Path::new(HIVE_COPY_PATH)).before_read())
 }
 
 /// How long after a failed connect the task tries again.
@@ -174,7 +173,7 @@ async fn read_permissions(
     swarm_queue_client::ensure_connected(client).ok()?;
     match tokio::time::timeout(READ_TIMEOUT, agent_permissions::read(client, agent)).await {
         Ok(Ok(agent_permissions::Read::Current(record))) => {
-            Some(HiveCopy::read_at(Path::new(HIVE_COPY_PATH)).after_read(agent, &record))
+            Some(HiveCopy::read_at(Path::new(HIVE_COPY_PATH)).after_read(&record))
         }
         Ok(Ok(agent_permissions::Read::NoBucket)) => None,
         Ok(Err(e)) => {