feat(ext/sw): org_add_config message + handler (device-local org config write)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01W3b8DA2mXmLWkd4zDbHXHg

extension/src/shared/error-copy.ts

@@ -101,6 +101,10 @@ export const ERROR_COPY: Record<string, ErrorCopy> = {
     cta: { label: 'Open setup', action: 'open_setup' },
   },
   // --- Org (enterprise) context errors (v0.9.0 Plan B) ---
+  org_already_configured: {
+    title: 'Already added',
+    body: 'That organization is already configured on this device.',
+  },
   org_not_configured: {
     title: 'Org not set up here',
     body: 'This organization is not configured on this device yet. Add it from the vault switcher before browsing its items.',

extension/src/shared/messages.ts

@@ -1,7 +1,7 @@
 import type {
   Item, ItemId, Manifest, ManifestEntry, VaultConfig, SetupState,
   DeviceSettings, GeneratorRequest, VaultSettings, AttachmentRef, Device,
-  FieldHistoryView, OrgConfigSummary, OrgManifestEntry, Collection,
+  FieldHistoryView, OrgConfig, OrgConfigSummary, OrgManifestEntry, Collection,
 } from './types';
 
 // --- Session timeout config ---
@@ -70,6 +70,7 @@ export type PopupMessage =
       referenceImageBytes: ArrayBuffer; deviceName: string }
   | { type: 'get_vault_status' }
   | { type: 'org_list_configs' }
+  | { type: 'org_add_config'; config: OrgConfig }
   | { type: 'org_switch'; context: string }
   | { type: 'org_list_items' }
   | { type: 'org_get_item'; id: string }
@@ -187,7 +188,7 @@ export const POPUP_ONLY_TYPES: ReadonlySet<PopupMessage['type']> = new Set([
   'preview_totp_from_secret',
   'generate_recovery_qr', 'unwrap_recovery_qr',
   'create_vault', 'attach_vault', 'get_vault_status',
-  'org_list_configs',
+  'org_list_configs', 'org_add_config',
   'org_switch', 'org_list_items', 'org_get_item', 'org_list_collections',
 ] as PopupMessage['type'][]);