Migrate to new @welshman/domain + instance-based @welshman/app API

Adopts the rewritten welshman API: the removed @welshman/util helpers
(Profile/List/Room/Handler/Encryptable) are now Reader/Builder classes in
@welshman/domain, and @welshman/app dropped its global singletons for an App
instance + app.use(Plugin) registry.

- src/app/welshman.ts is now the app bootstrap + session-state module (one shared
  App instance, multi-account sessions/login, app-wide reactive views) rather than
  a compat shim re-exporting the old globals.
- Rewrote ~100 callers to use app.use(Plugin) directly (thunks, profiles, relays,
  rooms, zaps, tags, wot, feeds, sync); thunk helpers are now thunk methods.
- Added @welshman/domain dependency.
- Resolved residual gaps (storage hydration via plugin.onItem/wrapManager/Plaintext,
  relay-list mutators, search-relay list, outbox #d filter).

Best-effort: no toolchain/linking available, so this is not build- or
type-checked. Remaining judgment calls are flagged with TODO(welshman-migration).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BsMjvv7krpZeHK1Njeneru

src/app/components/RoomMembersAdd.svelte

@@ -2,8 +2,8 @@
   import {onMount} from "svelte"
   import {setKey, popKey} from "@lib/implicit"
   import {sleep} from "@welshman/lib"
-  import {displayProfileByPubkey} from "@welshman/app"
-  import type {PublishedRoomMeta} from "@welshman/util"
+  import {Profiles} from "@welshman/app"
+  import {app} from "@app/welshman"
   import AltArrowLeft from "@assets/icons/alt-arrow-left.svg?dataurl"
   import Spinner from "@lib/components/Spinner.svelte"
   import Button from "@lib/components/Button.svelte"
@@ -42,7 +42,11 @@
       // Show loading for auto submit callback
       await sleep(500)
 
-      const error = await addRoomMembers(url, $room as PublishedRoomMeta, pubkeys)
+      // TODO(welshman-migration): addRoomMembers now expects a RoomMeta domain
+      // Reader, but deriveRoom yields the plain `Room` object. Passing it through
+      // as `any` preserves prior runtime behavior; verify Rooms.addMember accepts
+      // the plain Room shape (url/h/...) or resolve a real RoomMeta reader here.
+      const error = await addRoomMembers(url, $room as any, pubkeys)
 
       if (error) {
         pushToast({theme: "error", message: error})
@@ -72,7 +76,7 @@
         subtitle: "Automatically add members to space",
         message:
           nonSpaceMembers.length === 1
-            ? `${displayProfileByPubkey(nonSpaceMembers[0])} is not a member of this space. Add them?`
+            ? `${app.use(Profiles).display(nonSpaceMembers[0]).get()} is not a member of this space. Add them?`
             : `${nonSpaceMembers.length} people are not members of this space. Add them?`,
         confirm: async () => {
           setKey("RoomMembersAdd.confirm", true)