refactor: move WhatsApp channel implementation to extensions/ (#45725)

* refactor: move WhatsApp channel from src/web/ to extensions/whatsapp/

Move all WhatsApp implementation code (77 source/test files + 9 channel
plugin files) from src/web/ and src/channels/plugins/*/whatsapp* to
extensions/whatsapp/src/.

- Leave thin re-export shims at all original locations so cross-cutting
  imports continue to resolve
- Update plugin-sdk/whatsapp.ts to only re-export generic framework
  utilities; channel-specific functions imported locally by the extension
- Update vi.mock paths in 15 cross-cutting test files
- Rename outbound.ts -> send.ts to match extension naming conventions
  and avoid false positive in cfg-threading guard test
- Widen tsconfig.plugin-sdk.dts.json rootDir to support shim->extension
  cross-directory references

Part of the core-channels-to-extensions migration (PR 6/10).

* style: format WhatsApp extension files

* fix: correct stale import paths in WhatsApp extension tests

Fix vi.importActual, test mock, and hardcoded source paths that weren't
updated during the file move:
- media.test.ts: vi.importActual path
- onboarding.test.ts: vi.importActual path
- test-helpers.ts: test/mocks/baileys.js path
- monitor-inbox.test-harness.ts: incomplete media/store mock
- login.test.ts: hardcoded source file path
- message-action-runner.media.test.ts: vi.mock/importActual path

src/channels/plugins/normalize/whatsapp.ts

@@ -1,25 +1,2 @@
-import { normalizeWhatsAppTarget } from "../../../whatsapp/normalize.js";
-import { looksLikeHandleOrPhoneTarget, trimMessagingTarget } from "./shared.js";
-
-export function normalizeWhatsAppMessagingTarget(raw: string): string | undefined {
-  const trimmed = trimMessagingTarget(raw);
-  if (!trimmed) {
-    return undefined;
-  }
-  return normalizeWhatsAppTarget(trimmed) ?? undefined;
-}
-
-export function normalizeWhatsAppAllowFromEntries(allowFrom: Array<string | number>): string[] {
-  return allowFrom
-    .map((entry) => String(entry).trim())
-    .filter((entry): entry is string => Boolean(entry))
-    .map((entry) => (entry === "*" ? entry : normalizeWhatsAppTarget(entry)))
-    .filter((entry): entry is string => Boolean(entry));
-}
-
-export function looksLikeWhatsAppTargetId(raw: string): boolean {
-  return looksLikeHandleOrPhoneTarget({
-    raw,
-    prefixPattern: /^whatsapp:/i,
-  });
-}
+// Shim: re-exports from extensions/whatsapp/src/normalize.ts
+export * from "../../../../extensions/whatsapp/src/normalize.js";