feat(admin): restore org Agent role/skill management and fix 404 after project create

- explorer POST /projects now returns {id,name} matching the SPA contract
  (previously returned ProjectOnboardingResult.projectId, so res.id was
  undefined and the redirect to /projects/undefined 404'd)
- add OrganizationAgentConfiguration.listRoles/listSkills + AgentRoleRow/
  AgentSkillRow exports; upsertRole now returns the full row
- new agentConfigRoutes: GET/PUT /agent-roles, PUT /agent-roles/:id/skills,
  GET /agent-skills, GET /agent-models (env-default picker)
- restore admin-web roles page + RoleCard rewired to ADR-0017/0018 backend
  (label, defaultModel, tools whitelist, skill binding, systemPrompt,
  sortOrder, default toggle); add 角色 nav item + roles icon
- skill installation stays out-of-band (CLI/seed) per spec; the surface only
  lists installed skills and binds them to roles

hub/src/admin/routes/explorerRoutes.ts

@@ -155,7 +155,7 @@ export async function registerExplorerRoutes(
         workspaceRoot: config.projectWorkspaceRoot,
         ...(typeof body.folderId === "string" ? { folderId: body.folderId } : {}),
       });
-      return reply.status(201).send(result);
+      return reply.status(201).send({ id: result.projectId, name: body.name });
     } catch (err) {
       return handleRouteError(reply, err);
     }