feat(podcasts): render nostr-native podcast:person credits as real profiles

When a Podcasting-2.0 person's href points at an npub/nprofile (bare,
nostr: URI, or an njump-style link), upgrade the free-text credit to a real
Nostr profile: the standard ClickableUserPicture + UsernameDisplay, tappable
through to the profile. Plain web links keep the free-text card with the
default profile-image loader.

- quartz: PodcastPerson.nostrPubKey() resolves href → pubkey via Nip19Parser
  (npub/nprofile only). Covered by PodcastPersonSoundbiteTest.
- UI: PodcastPeople branches per person — LoadUser + standard profile
  components for nostr identities, free-text card otherwise — sharing one
  card scaffold so both look identical in the Hosts & Guests strip.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JGa1EM5KWyDo1o5Yr6sS18

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/PodcastEpisode.kt

@@ -200,7 +200,7 @@ fun RenderPodcastEpisode(
 
             if (!makeItShort) {
                 val persons = remember(noteEvent) { episode.episodePersons() }
-                PodcastPeople(persons, accountViewModel)
+                PodcastPeople(persons, accountViewModel, nav)
             }
 
             markdown?.takeIf { !makeItShort }?.let {

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/types/PodcastPeople.kt

@@ -33,6 +33,7 @@ import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
@@ -41,8 +42,14 @@ import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
 import com.vitorpamplona.amethyst.R
+import com.vitorpamplona.amethyst.model.User
 import com.vitorpamplona.amethyst.ui.components.RobohashFallbackAsyncImage
+import com.vitorpamplona.amethyst.ui.navigation.navs.INav
+import com.vitorpamplona.amethyst.ui.navigation.routes.routeFor
+import com.vitorpamplona.amethyst.ui.note.ClickableUserPicture
+import com.vitorpamplona.amethyst.ui.note.UsernameDisplay
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.AccountViewModel
+import com.vitorpamplona.amethyst.ui.screen.loggedIn.chats.rooms.LoadUser
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.amethyst.ui.theme.Size5dp
 import com.vitorpamplona.amethyst.ui.theme.grayText
@@ -50,14 +57,18 @@ import com.vitorpamplona.quartz.podcasts.PodcastPerson
 
 /**
  * A "Hosts & Guests" strip: the Podcasting-2.0 `podcast:person` credits for a show or episode,
- * rendered as a horizontally scrollable row of avatar + name + role. A person is free-text (not a
- * Nostr user), so we load their [PodcastPerson.img] with a robohash fallback seeded by their name,
- * and tapping one opens their [PodcastPerson.href] link when present.
+ * rendered as a horizontally scrollable row of avatar + name + role.
+ *
+ * A person is usually a free-text credit (name + image URL + web link), not a Nostr user, so it's
+ * drawn with the app's default profile-image loader and its link opens externally. But when the
+ * publisher's `href` points at an `npub`/`nprofile`, we upgrade the card to a real Nostr profile —
+ * the standard [ClickableUserPicture] + [UsernameDisplay], tappable through to the profile.
  */
 @Composable
 fun PodcastPeople(
     persons: List<PodcastPerson>,
     accountViewModel: AccountViewModel,
+    nav: INav,
 ) {
     val people = persons.filter { it.isValid() }
     if (people.isEmpty()) return
@@ -76,7 +87,7 @@ fun PodcastPeople(
             horizontalArrangement = Arrangement.spacedBy(12.dp),
         ) {
             items(people) { person ->
-                PersonItem(person, accountViewModel)
+                PersonItem(person, accountViewModel, nav)
             }
         }
     }
@@ -86,43 +97,101 @@ fun PodcastPeople(
 private fun PersonItem(
     person: PodcastPerson,
     accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    val pubKey = remember(person) { person.nostrPubKey() }
+
+    if (pubKey != null) {
+        LoadUser(pubKey, accountViewModel) { user ->
+            if (user != null) {
+                NostrPersonCard(user, person.role, accountViewModel, nav)
+            } else {
+                FreeTextPersonCard(person, accountViewModel)
+            }
+        }
+    } else {
+        FreeTextPersonCard(person, accountViewModel)
+    }
+}
+
+/** A person that resolved to a real Nostr identity — the standard profile treatment. */
+@Composable
+private fun NostrPersonCard(
+    user: User,
+    role: String?,
+    accountViewModel: AccountViewModel,
+    nav: INav,
+) {
+    PersonCardScaffold(
+        onClick = { nav.nav(routeFor(user)) },
+        role = role,
+        avatar = { ClickableUserPicture(user, 56.dp, accountViewModel) },
+        name = {
+            UsernameDisplay(
+                user,
+                Modifier.fillMaxWidth(),
+                textAlign = TextAlign.Center,
+                accountViewModel = accountViewModel,
+            )
+        },
+    )
+}
+
+/** A free-text `podcast:person` credit — default image loader, external link. */
+@Composable
+private fun FreeTextPersonCard(
+    person: PodcastPerson,
+    accountViewModel: AccountViewModel,
 ) {
     val uriHandler = LocalUriHandler.current
     val href = person.href
 
+    PersonCardScaffold(
+        onClick = href?.let { { runCatching { uriHandler.openUri(it) } } },
+        role = person.role,
+        avatar = {
+            RobohashFallbackAsyncImage(
+                robot = person.name,
+                model = person.img,
+                contentDescription = person.name,
+                modifier = Modifier.size(56.dp).clip(CircleShape),
+                loadProfilePicture = accountViewModel.settings.showProfilePictures(),
+                loadRobohash = accountViewModel.settings.isNotPerformanceMode(),
+            )
+        },
+        name = {
+            Text(
+                text = person.name,
+                style = MaterialTheme.typography.labelMedium,
+                maxLines = 1,
+                overflow = TextOverflow.Ellipsis,
+                textAlign = TextAlign.Center,
+                modifier = Modifier.fillMaxWidth(),
+            )
+        },
+    )
+}
+
+/** Shared 72dp centered card layout: avatar, name, and an optional role line. */
+@Composable
+private fun PersonCardScaffold(
+    onClick: (() -> Unit)?,
+    role: String?,
+    avatar: @Composable () -> Unit,
+    name: @Composable () -> Unit,
+) {
     Column(
         modifier =
             Modifier
                 .width(72.dp)
-                .then(
-                    if (href != null) {
-                        Modifier.clickable { runCatching { uriHandler.openUri(href) } }
-                    } else {
-                        Modifier
-                    },
-                ).padding(vertical = 4.dp),
+                .then(if (onClick != null) Modifier.clickable(onClick = onClick) else Modifier)
+                .padding(vertical = 4.dp),
         horizontalAlignment = Alignment.CenterHorizontally,
         verticalArrangement = Arrangement.spacedBy(4.dp),
     ) {
-        RobohashFallbackAsyncImage(
-            robot = person.name,
-            model = person.img,
-            contentDescription = person.name,
-            modifier = Modifier.size(56.dp).clip(CircleShape),
-            loadProfilePicture = accountViewModel.settings.showProfilePictures(),
-            loadRobohash = accountViewModel.settings.isNotPerformanceMode(),
-        )
-
-        Text(
-            text = person.name,
-            style = MaterialTheme.typography.labelMedium,
-            maxLines = 1,
-            overflow = TextOverflow.Ellipsis,
-            textAlign = TextAlign.Center,
-            modifier = Modifier.fillMaxWidth(),
-        )
-
-        person.role?.takeIf { it.isNotEmpty() }?.let {
+        avatar()
+        name()
+        role?.takeIf { it.isNotEmpty() }?.let {
             Text(
                 text = it,
                 style = MaterialTheme.typography.labelSmall,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/podcasts/PodcastHeader.kt

@@ -139,7 +139,7 @@ fun PodcastHeader(
             }
 
             val persons = remember(show) { show?.showPersons() ?: emptyList() }
-            PodcastPeople(persons, accountViewModel)
+            PodcastPeople(persons, accountViewModel, nav)
         }
 
         // Standard engagement row for the show itself (comment / zap / react), like any other

quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/podcasts/PodcastPerson.kt

@@ -21,6 +21,10 @@
 package com.vitorpamplona.quartz.podcasts
 
 import androidx.compose.runtime.Immutable
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip19Bech32.Nip19Parser
+import com.vitorpamplona.quartz.nip19Bech32.entities.NProfile
+import com.vitorpamplona.quartz.nip19Bech32.entities.NPub
 import kotlinx.serialization.Serializable
 
 /**
@@ -46,4 +50,18 @@ class PodcastPerson(
     val href: String? = null,
 ) {
     fun isValid() = name.isNotBlank()
+
+    /**
+     * The Nostr pubkey (hex) this person points at, when [href] is (or embeds) an `npub`/`nprofile`
+     * — including `nostr:` URIs and `njump.me`-style links. Null for a plain web link or no href.
+     * Lets a client upgrade a free-text credit to a real Nostr profile when the publisher linked one.
+     */
+    fun nostrPubKey(): HexKey? =
+        href?.let {
+            when (val entity = Nip19Parser.uriToRoute(it)?.entity) {
+                is NPub -> entity.hex
+                is NProfile -> entity.hex
+                else -> null
+            }
+        }
 }

quartz/src/commonTest/kotlin/com/vitorpamplona/quartz/nipXXPodcasting20/PodcastPersonSoundbiteTest.kt

@@ -75,6 +75,20 @@ class PodcastPersonSoundbiteTest {
         assertNull(PersonTag.parse(arrayOf("person", "")))
     }
 
+    @Test
+    fun `person href resolves an npub to a pubkey`() {
+        val npub = "npub1hv7k2s755n697sptva8vkh9jz40lzfzklnwj6ekewfmxp5crwdjs27007y"
+        val hex = "bb3d6543d4a4f45f402b674ecb5cb2155ff12456fcdd2d66d9727660d3037365"
+        assertEquals(hex, PodcastPerson(name = "Alice", href = npub).nostrPubKey())
+        assertEquals(hex, PodcastPerson(name = "Alice", href = "nostr:$npub").nostrPubKey())
+    }
+
+    @Test
+    fun `person href that is a plain web link has no pubkey`() {
+        assertNull(PodcastPerson(name = "Alice", href = "https://alice.example").nostrPubKey())
+        assertNull(PodcastPerson(name = "Alice", href = null).nostrPubKey())
+    }
+
     @Test
     fun `soundbite tag parses times and optional title`() {
         val soundbite = SoundbiteTag.parse(arrayOf("soundbite", "73.5", "60.0", "Best moment"))