finish phase 3: type-only codemod and zero non-bridge @atproto/api imports

Task 8: codemod repointed 150 namespace-type files to #/lexicons
(AppBskyFeedDefs.PostView -> app.bsky.feed.defs.PostView, .Record -> .Main)
plus ~105 hand-fixed consumers (composer/video state, DebugMod, Profile,
onboarding, dialogs). DM_SERVICE_HEADERS deleted; last chat call sites on
the chat client. RichText.tsx flipped to SDK-only. Remaining @atproto/api
importers: the three session bridge files, the deliberate dual-world
matcher in lib/xrpc-error.ts, and test fixtures. toLex boundary casts are
TODO(phase4)-tagged for bridge removal.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/features/liveEvents/preferences.ts

@@ -14,7 +14,7 @@ import {
   type LiveEventFeed,
   type LiveEventFeedMetricContext,
 } from '#/features/liveEvents/types'
-import {app} from '#/lexicons'
+import {type app} from '#/lexicons'
 
 export type LiveEventPreferencesAction = Parameters<
   typeof updateLiveEventPreferences