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/comments.ts

@@ -1,6 +1,7 @@
 import type {TrustedEvent} from "@welshman/util"
 import {COMMENT, makeEvent} from "@welshman/util"
-import {publishThunk, tagEventForComment} from "@welshman/app"
+import {Thunks, Tags} from "@welshman/app"
+import {app} from "@app/welshman"
 
 export type CommentParams = {
   event: TrustedEvent
@@ -10,7 +11,7 @@ export type CommentParams = {
 }
 
 export const makeComment = ({url, event, content, tags = []}: CommentParams) =>
-  makeEvent(COMMENT, {content, tags: [...tags, ...tagEventForComment(event, url)]})
+  makeEvent(COMMENT, {content, tags: [...tags, ...app.use(Tags).tagEventForComment(event, url)]})
 
 export const publishComment = ({relays, ...params}: CommentParams & {relays: string[]}) =>
-  publishThunk({event: makeComment({url: relays[0], ...params}), relays})
+  app.use(Thunks).publish({event: makeComment({url: relays[0], ...params}), relays})