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/reactions.ts

@@ -1,6 +1,7 @@
 import type {TrustedEvent} from "@welshman/util"
 import {REACTION, getTag, makeEvent} from "@welshman/util"
-import {publishThunk, tagEventForReaction} from "@welshman/app"
+import {Thunks, Tags} from "@welshman/app"
+import {app} from "@app/welshman"
 import {PROTECTED} from "@app/groups"
 
 export type ReactionParams = {
@@ -18,7 +19,7 @@ export const makeReaction = ({
   event,
   tags: paramTags = [],
 }: ReactionParams) => {
-  const tags = [...paramTags, ...tagEventForReaction(event, url)]
+  const tags = [...paramTags, ...app.use(Tags).tagEventForReaction(event, url)]
   const groupTag = getTag("h", event.tags)
 
   if (groupTag) {
@@ -33,5 +34,5 @@ export const makeReaction = ({
 }
 
 export const publishReaction = ({relays, ...params}: ReactionParams & {relays: string[]}) => {
-  publishThunk({event: makeReaction({url: relays[0], ...params}), relays})
+  app.use(Thunks).publish({event: makeReaction({url: relays[0], ...params}), relays})
 }