feat: show external-id scope as reply context for NIP-22 comments

A Comment event (kind 1111) scoped to an external identifier (`I` tag)
previously rendered as a bare text post and landed in the Home "New
Threads" feed. Treat it as a reply to that external scope: it now shows
in the conversations feed and renders a typed chip (hashtag, geohash,
url, or generic) above the comment text.

https://claude.ai/code/session_01ArHkNXu1ANrVGZAyMWg4Xu

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/nip22Comments/CommentEvent.kt

@@ -181,6 +181,9 @@ class CommentEvent(
 
     fun isScoped(scopeTest: (String) -> Boolean) = tags.any { RootIdentifierTag.isTagged(it, scopeTest) || ReplyIdentifierTag.isTagged(it, scopeTest) }
 
+    /** True when the comment points at an external identifier (`I` tag), e.g. a hashtag, geohash or url. */
+    fun hasRootScopeIdentifier() = tags.any(RootIdentifierTag::match)
+
     fun hasRootScopeKind(kind: String) = tags.any(RootKindTag::isKind, kind)
 
     fun hasReplyScopeKind(kind: String) = tags.any(ReplyKindTag::isKind, kind)