[management] Add Agent Network access roles and self-service endpoints (#7221)

Delegating Agent Network today means handing out full account admin, and
regular users cannot see their own usage or how to connect a local tool.

Add two roles on top of the existing agent_network permission
submodules. agent_network_admin owns the whole area (providers,
policies, guardrails, budgets, usage, logs, settings) with read-only
users, groups, peers, and account info needed to build policies, and
nothing else in the account. usage_viewer is the regular User baseline
plus read on the aggregated usage and cost overview: no provider
configuration, no policies, no request-level logs, which can contain
captured prompts. billing_admin gets a proper permission-map entry with
the User baseline so role resolution stops failing with role-not-found;
its plan and invoice permissions stay enforced cloud-side.

Add the self-service endpoints behind the "My Agent Network" view,
available to every authenticated user because both answers are scoped
strictly to the caller. GET /api/agent-network/me/setup returns the
account endpoint plus the providers and models the caller's own groups
authorize, computed with the same rules the proxy enforces: policy
filtering as in policy selection, model allowlist union intersected
with declared models, orphan and disabled providers omitted. Not set up
and no access are deliberately indistinguishable, and the response
carries display metadata only. GET /api/agent-network/me/consumption
returns the caller's own user-dimension counters.

agent-network/README.md

@@ -96,6 +96,42 @@ components:
   — the management-side control plane: providers, policies, guardrails, limits, routing,
   and usage/access logs.
 
+## Access roles
+
+Agent Network permissions build on the account permission matrix
+([`management/server/permissions/`](../management/server/permissions)). The
+`agent_network` area is split into dotted submodules (`agent_network.providers`,
+`.policies`, `.guardrails`, `.budgets`, `.usage`, `.logs`, `.settings`); a role may
+grant a single submodule or the parent, which cascades to all of them.
+
+Two roles delegate Agent Network access without account-admin rights:
+
+- **`agent_network_admin`** — full control over the whole `agent_network` area plus
+  read-only users, groups, peers, and account info (needed to build policies).
+  Nothing else in the account.
+- **`usage_viewer`** — the regular User baseline plus read on
+  `agent_network.usage` (the aggregated usage and cost overview) and read-only
+  access to the resources the usage filters resolve against: users, groups,
+  peers, and the provider list (connection config redacted — no upstream URLs
+  or operator-supplied header values). No policies, and no account-wide
+  request-level access logs; like any caller, it still reads its own requests
+  through the self-scoped endpoints below.
+
+Every authenticated user, regardless of role, can read the caller-scoped
+self-service endpoint `GET /api/agent-network/agent-config` (the endpoint, providers,
+and models the caller's own policies allow — what a local AI tool needs and nothing
+more). The regular usage and access-log endpoints self-scope instead of denying:
+a caller without the account-wide grant gets their own rows back, so "my usage"
+and "my requests" are the same endpoints the admin dashboard uses. The provider
+list self-scopes the same way — a caller without the providers grant gets the
+providers their own policies authorize, reduced to the display surface, with
+each provider's model list cut to what the caller's policy guardrails and the
+provider's declared models effectively permit (the same computation the setup
+answer and the proxy use). This feeds the dashboard's provider and model
+filters. Role
+definitions live in
+[`management/server/permissions/roles/`](../management/server/permissions/roles).
+
 ## Documentation
 
 Full documentation, architecture, and quickstart: