feat(sdk): P4.5 @insignia/iios-support-web (composes message-web + support REST)

SupportProvider (wraps MessageProvider + support client); useEscalate, useTickets/
useAssignedTickets (+createTicket/patch), useCallbackRequest, useAvailability;
re-exports useThread/useMessages. Boundary allowlist: support-web -> contracts+
kernel-client+message-web+inbox-web.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/check-import-boundary.mjs

@@ -20,6 +20,12 @@ const ALLOWED = {
   '@insignia/iios-service': ['@insignia/iios-contracts', '@insignia/iios-testkit'],
   '@insignia/iios-message-web': ['@insignia/iios-contracts', '@insignia/iios-kernel-client'],
   '@insignia/iios-inbox-web': ['@insignia/iios-contracts', '@insignia/iios-kernel-client'],
+  '@insignia/iios-support-web': [
+    '@insignia/iios-contracts',
+    '@insignia/iios-kernel-client',
+    '@insignia/iios-message-web',
+    '@insignia/iios-inbox-web',
+  ],
 };
 const KNOWN = Object.keys(ALLOWED);