Add org switcher with create, switch, and delete

The sidebar org button was inert: clicking it did nothing. Add a real
dropdown menu listing every organization, a "New organization" entry
that re-enters onboarding without resetting the database, and a per-org
delete affordance with inline confirmation. Active org is now persisted
in a single-row app_state table so the snapshot keeps a stable
selection across restarts and the renderer drives switching via two new
IPC channels (setActiveOrganization, deleteOrganization).

- migration 006 adds app_state(id=1, active_org_id, updated_at)
- snapshot resolves active org from app_state with the first-org fallback
- OrganizationService gains setActive + delete + bootstrap upsert
- new OrgSwitcher renderer component keeps Shell.tsx lean

AgentCompany-New/src/shared/commands.ts

@@ -6,6 +6,14 @@ import type {
   TaskStatus,
 } from "./domain";
 
+export interface SetActiveOrganizationInput {
+  orgId: string;
+}
+
+export interface DeleteOrganizationInput {
+  orgId: string;
+}
+
 export interface CreateOrganizationInput {
   organizationName: string;
   description?: string;