fix(robustness): surface swallowed persistence-write failures + federation tombstone durability

§C of the 1.8.0 hardening plan: persistence writes whose Results were
silently dropped now log a warn/error with context (mesh contact
blocklist, scheduler state, content catalog, container registry,
update state, bitcoin relay, package install markers, server shutdown
state). §I: federation tombstones are now flushed durably in
storage/sync so cleared peers can't resurrect after a crash.

Tracker updated with shas in docs/1.8.0-RELEASE-HARDENING-PLAN.md.

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

core/archipelago/src/api/rpc/package/install.rs

@@ -32,6 +32,8 @@ pub(in crate::api::rpc) async fn install_log(msg: &str) {
         .open(INSTALL_LOG)
         .await
     {
+        // Fire-and-forget by design: install-log lines are advisory, and a
+        // per-line warn would spam the very log stream that's failing.
         let _ = f.write_all(line.as_bytes()).await;
     }
 }