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.

docs/turn-loop/README.md

@@ -177,7 +177,7 @@ harness between turns.
 One harness serve binary (`hive-agent`, with its `hive-agent-mcp`
 sibling), one shared `nix/agent-modules/` tree, one service unit
 (`systemd.services.hive-agent`) for all agents. Privilege
-differences live server-side in the broker socket (which tool groups
+differences live in the agent's swarm permissions and the broker socket (which tools
 and manager-surface calls each agent receives).
 
 `agent.nix` and `ruth.nix` both import the shared `nix/agent-modules/`.
@@ -250,7 +250,7 @@ The rest lives alongside this page, in three topic files:
   custom static files, connectivity overrides, claude plugins, cargo message
   filtering).
 - **[mcp.md](mcp.md)** — the MCP tool surface claude sees: core tools,
-  privileged tool groups, self-wake, authoritative state, the tool envelope,
+  permission-gated tools, self-wake, authoritative state, the tool envelope,
   and the built-in tool allowlist.
 
 Per-subsystem impl detail lives in each module's `//!` doc-comment; these pages