initial: notify v0.1.0 — tag-based player-message routing

Tag-based messages, channel registry, tag-filter routing (OR-list,
empty=catch-all), per-channel history ring-buffer, subscriber callbacks,
severity sugar wrappers (info/warn/error), and engine.print mirror.

manifest.lib

@@ -0,0 +1 @@
+{"id":"lib-core.notify","version":"0.1.0","api_min":"0.1","deps":[]}