Add buzz 0.5.28: Block's desktop workspace for humans and agents (#919)

Buzz (https://github.com/block/buzz, Apache-2.0) is a Tauri desktop app
on a Nostr relay. Upstream ships Linux builds for x86_64 only, so this
builds the desktop-v0.5.28 tag from source for x86_64 and aarch64,
following upstream's release-linux job: the six sidecar binaries from
the root workspace, then the app with --features mesh-llm. The updater
stays compiled out (its key and endpoint are unset), so pacman owns
updates. On the fast ring; the watch follows desktop-v* releases.

On aarch64, -march gains +crypto so sha2-asm can assemble its SHA
instructions; sha2 still detects them at runtime.

Built natively for aarch64 with bin/build and launched with isolated
HOME/XDG dirs: the window opens and renders the bundled frontend.

pkgbuilds/buzz/.omarchy/package.json

@@ -0,0 +1,10 @@
+{
+  "source": "local",
+  "release_ring": "fast",
+  "upstream": {
+    "watch": {
+      "github": "block/buzz",
+      "pattern": "desktop-v(?P<version>[0-9]+(?:\\.[0-9]+)*)"
+    }
+  }
+}