fix: remove unused import and correct WhatsApp/Email registry status

- Remove unused `std::fmt::Write` import in `load_openclaw_bootstrap_files`
  (eliminates compiler warning)
- Update WhatsApp integration status from ComingSoon to config-driven
  (implementation exists in channels/whatsapp.rs)
- Update Email integration status from ComingSoon to config-driven
  (implementation exists in channels/email_channel.rs)
- Update tests to reflect corrected integration statuses

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/channels/mod.rs

@@ -78,7 +78,6 @@ fn spawn_supervised_listener(
 
 /// Load OpenClaw format bootstrap files into the prompt.
 fn load_openclaw_bootstrap_files(prompt: &mut String, workspace_dir: &std::path::Path) {
-    use std::fmt::Write;
     prompt.push_str("The following workspace files define your identity, behavior, and context.\n\n");
 
     let bootstrap_files = [