feat(whatsapp): add sendReadReceipts config option

Add option to disable automatic read receipts for WhatsApp messages.
When set to false, Clawdbot will not mark messages as read (blue ticks).

Closes #344

Changes:
- Add sendReadReceipts to WhatsAppConfig and WhatsAppAccountConfig types
- Add sendReadReceipts to zod schemas for validation
- Add sendReadReceipts to ResolvedWhatsAppAccount with fallback chain
- Pass sendReadReceipts through to monitorWebInbox
- Gate sock.readMessages() call based on config option

Default behavior (true) is preserved - only explicitly setting false
will disable read receipts.

src/config/types.whatsapp.ts

@@ -14,6 +14,8 @@ export type WhatsAppConfig = {
   capabilities?: string[];
   /** Allow channel-initiated config writes (default: true). */
   configWrites?: boolean;
+  /** Send read receipts for incoming messages (default true). */
+  sendReadReceipts?: boolean;
   /**
    * Inbound message prefix (WhatsApp only).
    * Default: `[{agents.list[].identity.name}]` (or `[clawdbot]`) when allowFrom is empty, else `""`.
@@ -84,6 +86,8 @@ export type WhatsAppAccountConfig = {
   configWrites?: boolean;
   /** If false, do not start this WhatsApp account provider. Default: true. */
   enabled?: boolean;
+  /** Send read receipts for incoming messages (default true). */
+  sendReadReceipts?: boolean;
   /** Inbound message prefix override for this account (WhatsApp only). */
   messagePrefix?: string;
   /** Override auth directory (Baileys multi-file auth state). */