agent permissions: one set, tool groups included, set at agent creation

mara on #5170: "dont split caps and perms. its all perms. / dont include
the now empty tool groups / nothing set -> default / also add perms to
agent creation screen".

- hive-sh4re: one `Permission` enum (messaging, meta, inbox, execution,
  web_tools, manage_root_agent) replaces `ToolGroup` and `Capability`;
  `lifecycle`/`forge` are gone. `Permission::default_for` is the default
  for an agent the swarm sets nothing for.
- The record is `{ "permissions": [...] }`. Missing key, unset field or
  no successful read yet = default; `[]` = none; a failed read after a
  good one keeps the last value.
- hive-agent reads its own key every 10s and builds each turn's --tools,
  --allowedTools and MCP config (rewritten before every turn) from it;
  the subagent daemon reads it on each start/continue. Agents get a
  read-only grant on their own key.
- hive-c0re restarts an agent only when its manage_root_agent changes.
  The import now merges meta/capabilities.json and meta/tool-groups.json
  into one list per agent and deletes both; the "import pending, don't
  read" decision is `ImportOutcome::read_allowed`, table-tested.
- swarm-controller: `GET /api/permissions` (names + default) and an
  optional `permissions` on `POST /api/agents`, stored before the job is
  queued. swarm-ui's create-agent form gets a permissions field.
- Deleted: HIVE_TOOL_GROUPS and its forward to the subagent daemon,
  tool_groups.rs, ruth's tool-group seed, the permissions rebuild job
  (PermPayload/WritePermFile/perm_change), the dashboard permissions tab
  and its stale-entries panel.

Part of #5170.

hive-c0re/src/agent_config/topology.rs

@@ -9,11 +9,11 @@
 //! 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
+//! [`hive_sh4re::permissions::Permission::ManageRootAgent`] holder gets
 //! bind-mounted ([`all_agents`]).
 //!
 //! Broader-than-your-own bind-mount grants are **not** stored here: they
-//! hang off the `ManageRootAgent` capability the swarm grants
+//! hang off the `ManageRootAgent` permission the swarm grants
 //! (`swarm_permissions`). See
 //! `lifecycle::set_nspawn_flags`.
 
@@ -65,7 +65,7 @@ fn read_from(path: &Path) -> std::io::Result<BTreeSet<String>> {
 }
 
 /// Every agent the roster knows about, in name order. This is the set
-/// a [`hive_sh4re::permissions::Capability::ManageRootAgent`] holder gets
+/// a [`hive_sh4re::permissions::Permission::ManageRootAgent`] holder gets
 /// bind-mounted, and it is deliberately unfiltered: that capability means
 /// "may manage any agent", so the set is all of them.
 ///