fix(coderd): allow non-admin users to list chat model configs (#22407)

## Problem

Non-admin users of the Agents (chat) feature send `model_config_id:
"00000000-0000-0000-0000-000000000000"` (nil UUID) when creating chats,
because the `GET /api/experimental/chats/model-configs` endpoint
requires `policy.ActionRead` on `rbac.ResourceDeploymentConfig`, which
is only granted to admins.

The flow:
1. `AgentsPage.tsx` calls `useQuery(chatModelConfigs())` → hits
`listChatModelConfigs`
2. Non-admin users get a **403 Forbidden** response
3. `chatModelConfigsQuery.data` is `undefined`, so the
`modelConfigIDByModelID` map is empty
4. `handleCreateChat` falls back to `nilUUID` for `model_config_id`
5. The backend rejects the nil UUID: `"Invalid model config ID."`

## Fix

Changed `listChatModelConfigs` to allow all authenticated users to read
model configs:
- **Admin users** continue to see all configs (including disabled ones)
for management via `GetChatModelConfigs`
- **Non-admin users** now see only enabled configs via
`GetEnabledChatModelConfigs` with a system context, which is sufficient
for using the chat feature

This follows the same pattern as `listChatModels`, which already uses
`dbauthz.AsSystemRestricted(ctx)` to allow all authenticated users to
see available models.

Write endpoints (create/update/delete) retain their existing
`ResourceDeploymentConfig` authorization.

## Testing

- Updated `TestListChatModelConfigs/ForbiddenForOrganizationMember` →
`SuccessForOrganizationMember` to verify non-admin users can list
enabled model configs
- All existing chat tests continue to pass

coderd/chats.go

@@ -2444,12 +2444,20 @@ func (api *API) deleteChatProvider(rw http.ResponseWriter, r *http.Request) {
 
 func (api *API) listChatModelConfigs(rw http.ResponseWriter, r *http.Request) {
 	ctx := r.Context()
-	if !api.Authorize(r, policy.ActionRead, rbac.ResourceDeploymentConfig) {
-		httpapi.Forbidden(rw)
-		return
-	}
 
-	configs, err := api.Database.GetChatModelConfigs(ctx)
+	// Admin users can see all model configs (including disabled ones)
+	// for management purposes. Non-admin users see only enabled
+	// configs, which is sufficient for using the chat feature.
+	isAdmin := api.Authorize(r, policy.ActionRead, rbac.ResourceDeploymentConfig)
+
+	var configs []database.ChatModelConfig
+	var err error
+	if isAdmin {
+		configs, err = api.Database.GetChatModelConfigs(ctx)
+	} else {
+		//nolint:gocritic // All authenticated users need to read enabled model configs to use the chat feature.
+		configs, err = api.Database.GetEnabledChatModelConfigs(dbauthz.AsSystemRestricted(ctx))
+	}
 	if err != nil {
 		httpapi.Write(ctx, rw, http.StatusInternalServerError, codersdk.Response{
 			Message: "Failed to list chat model configs.",

coderd/chats_test.go

@@ -818,16 +818,29 @@ func TestListChatModelConfigs(t *testing.T) {
 		require.True(t, found)
 	})
 
-	t.Run("ForbiddenForOrganizationMember", func(t *testing.T) {
+	t.Run("SuccessForOrganizationMember", func(t *testing.T) {
 		t.Parallel()
 
 		ctx := testutil.Context(t, testutil.WaitLong)
 		adminClient := newChatClient(t)
 		firstUser := coderdtest.CreateFirstUser(t, adminClient)
+		modelConfig := createChatModelConfig(t, adminClient)
 		memberClient, _ := coderdtest.CreateAnotherUser(t, adminClient, firstUser.OrganizationID)
 
-		_, err := memberClient.ListChatModelConfigs(ctx)
-		requireSDKError(t, err, http.StatusForbidden)
+		// Non-admin users should see only enabled model configs.
+		configs, err := memberClient.ListChatModelConfigs(ctx)
+		require.NoError(t, err)
+		require.NotEmpty(t, configs)
+
+		found := false
+		for _, config := range configs {
+			if config.ID == modelConfig.ID {
+				found = true
+				require.Equal(t, "openai", config.Provider)
+				require.Equal(t, "gpt-4o-mini", config.Model)
+			}
+		}
+		require.True(t, found)
 	})
 }