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.

docs/agent-lifecycle/agent-roster.md

@@ -78,9 +78,9 @@ module docs for the exact call chain.
 
 ## Hard-coded manager behaviour
 
-The **manager (`ruth`)** differs from other agents in naming/bootstrap,
-its socket flavour and its default permissions; its prompt, tool
-allow-list and state dirs work as for every other agent.
+The **manager (`ruth`)** differs from other agents in naming/bootstrap
+and its socket flavour; its permissions, prompt, tool allow-list and
+state dirs work as for every other agent.
 
 <!-- vale write-good.Passive = NO -->
 
@@ -97,13 +97,13 @@ allow-list and state dirs work as for every other agent.
   both flavours; matrix, bash and forge don't call it — their
   notifications push a todo on the harness's in-agent socket (see
   [`docs/turn-loop/mcp.md`](../turn-loop/mcp.md#waking-the-agent-from-inside-the-container)).
-- **Storage/mounts** — the manager container gets
+- **Storage/mounts** — the `manage_root_agent` permission, which the swarm
+  UI's setup assistant creates ruth with, gets a container
   `/var/lib/hyperhive/agents` bind-mounted RW at `/agents` (so it can
   manage any agent's state dir — config isn't authored there, since a
   real config change is a PR from a clone), plus RO mounts for
   `/applied` (diff against what's deployed) and `/meta` (system-wide
-  deploy log). That grant is the `manage_root_agent` permission: ruth
-  holds it by default, and any agent holding it gets the same mounts.
+  deploy log). Any agent holding it gets the same mounts.
   The operator dashboard's `POST /api/meta-update` is the only path
   that writes `flake.lock`.
 - **Prompt** — identical for every container: `prompts/system.md`
@@ -115,8 +115,8 @@ allow-list and state dirs work as for every other agent.
   (`filter_role_blocks(SAMPLE, "manager")`).
 - **Tool allow-list** — the MCP tools claude sees come from the agent's
   permissions alone, the same mechanism for every agent
-  ([`docs/turn-loop/mcp.md`](../turn-loop/mcp.md)). Ruth's default
-  permissions add only `manage_root_agent` (`Permission::default_for`).
+  ([`docs/turn-loop/mcp.md`](../turn-loop/mcp.md)). Ruth's permissions
+  are the default plus `manage_root_agent`, stored for her like any grant.
 - **State dirs** — _not_ special-cased: `HYPERHIVE_STATE_DIR` is
 injected uniformly via `systemd.globalEnvironment` for every
 container including the manager, so all token/state paths resolve

docs/agent-lifecycle/config-changes.md

@@ -270,10 +270,13 @@ dirs.
 ⚠️ nspawn bakes bind flags at container start, so hive-c0re restarts
 an agent, after its current turn, when its `manage_root_agent` changes.
 
-The root agent holds the permission by default: an agent whose record
-leaves `permissions` unset gets the default, which includes
-`manage_root_agent` for `ruth` and for no other agent. Setting her
-permissions without it revokes it.
+No agent holds the permission by default: an agent whose record leaves
+`permissions` unset gets the default, which doesn't include
+`manage_root_agent`, whatever the agent's name. The swarm UI's setup
+assistant creates ruth with it. For a ruth that predates that, whose
+permissions were unset, swarm-controller writes the default plus
+`manage_root_agent` into her key once at start, so she keeps her mounts;
+it never touches a key that's already set.
 
 Each proposed repo (`/agents/<n>/config/`) is pre-configured
 with `applied` as a git remote pointing at
@@ -331,8 +334,10 @@ Differences from sub-agents:
   (vs `agent-base`).
 - Web UI port via `lifecycle::agent_web_port("ruth")` — same
   FNV-1a hash as every other agent (8100..8999 range).
-- `set_nspawn_flags` adds two extra binds: `/var/lib/hyperhive/agents`
-  → `/agents` (RW) so the root agent can edit per-agent proposed repos,
+- The root agent holds `manage_root_agent` (the swarm UI's setup
+  assistant creates her with it), for which `set_nspawn_flags` adds two extra binds:
+  `/var/lib/hyperhive/agents` → `/agents` (RW) so the root agent can edit
+  per-agent proposed repos,
   and `/var/lib/hyperhive/applied` → `/applied` (RO) so the root agent
   can `git fetch` deployed/failed/denied tags from any agent's
   authoritative applied repo (see "Root-agent view of applied" below).

docs/agent-lifecycle/persistence.md

@@ -408,7 +408,8 @@ Contents:
   to live here; nothing reads or writes it now. An old copy in the meta repo
   is harmless and you can delete it.
 
-The root agent has the meta dir RO-mounted at `/meta/`.
+An agent holding `manage_root_agent`, normally ruth, has the meta dir
+RO-mounted at `/meta/`.
 
 Outside the meta repo, `/var/lib/hyperhive/swarm-agent-permissions.json`
 holds the permissions the swarm grants this hive's agents, as