feat: pin followed geohash channels to the bottom nav

Adds a "Location Channels" category to the bottom-bar settings picker so a
user can pin their joined geohash cells as avatars alongside PublicChat,
RelayGroup and Concord groups. Each pinned cell renders a location-pin
robohash keyed by the geohash, labelled "#<cell>", opening the location
chat when tapped.

- BottomBarEntry.Geohash sealed variant (+ stable key)
- NavBarItem.GEOHASH_CHATS catalog entry in the chats category
- rememberGeohashEntryDisplay resolves the anonymous avatar/route (no
  metadata REQ — the cell is anonymous by design)
- picker/settings and live-bar group branches route geohash through the
  shared GroupEntryDisplay path
- no feed preloader (the cell's message subscription opens from the chat
  screen itself)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0172JoMccseEKenyWan6txWV

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/bottombars/AppBottomBar.kt

@@ -236,6 +236,7 @@ internal fun rememberBottomBarSlot(
         is BottomBarEntry.PublicChat,
         is BottomBarEntry.RelayGroup,
         is BottomBarEntry.Concord,
+        is BottomBarEntry.Geohash,
         -> {
             val display = rememberGroupEntryDisplay(entry, accountViewModel) ?: return null
             // A pinned chat/group shows its avatar, like the favorite-app tabs — icon only.

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/bottombars/BottomBarEntry.kt

@@ -76,6 +76,13 @@ sealed interface BottomBarEntry {
     data class Concord(
         val communityId: String,
     ) : BottomBarEntry
+
+    /** A pinned Bitchat geohash location channel, keyed by its geohash cell; opens the location chat. */
+    @Serializable
+    @SerialName("geohash")
+    data class Geohash(
+        val geohash: String,
+    ) : BottomBarEntry
 }
 
 /**
@@ -90,6 +97,7 @@ val BottomBarEntry.stableKey: String
             is BottomBarEntry.PublicChat -> "publicChat:$channelId"
             is BottomBarEntry.RelayGroup -> "relayGroup:$relayUrl|$groupId"
             is BottomBarEntry.Concord -> "concord:$communityId"
+            is BottomBarEntry.Geohash -> "geohash:$geohash"
         }
 
 /** The favorite-app ids in this bottom-bar config — the apps that should be kept warm as bottom-row tabs. */

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/bottombars/GroupBottomBarEntries.kt

@@ -172,6 +172,21 @@ fun rememberConcordEntryDisplay(
     )
 }
 
+/**
+ * A pinned geohash location channel. Anonymous by design — no metadata REQ; the row is a location
+ * pin robohash keyed by the cell, labelled with the geohash, opening the location chat.
+ */
+@Composable
+fun rememberGeohashEntryDisplay(entry: BottomBarEntry.Geohash): GroupEntryDisplay =
+    remember(entry.geohash) {
+        GroupEntryDisplay(
+            label = "#${entry.geohash}",
+            robotSeed = entry.geohash,
+            model = null,
+            route = Route.GeohashChat(entry.geohash),
+        )
+    }
+
 /**
  * Resolves any chat/group entry to its live display, or null for a non-group entry. [subscribe] is
  * forwarded to the channel observers: true (the default) keeps a relay REQ open — used by the live
@@ -187,6 +202,7 @@ fun rememberGroupEntryDisplay(
         is BottomBarEntry.PublicChat -> rememberPublicChatEntryDisplay(entry, accountViewModel, subscribe)
         is BottomBarEntry.RelayGroup -> rememberRelayGroupEntryDisplay(entry, accountViewModel, subscribe)
         is BottomBarEntry.Concord -> rememberConcordEntryDisplay(entry, accountViewModel)
+        is BottomBarEntry.Geohash -> rememberGeohashEntryDisplay(entry)
         is BottomBarEntry.BuiltIn -> null
         is BottomBarEntry.Favorite -> null
     }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/navigation/bottombars/NavBarItem.kt

@@ -68,6 +68,7 @@ enum class NavBarItem {
     PUBLIC_CHATS,
     RELAY_GROUPS,
     CONCORD,
+    GEOHASH_CHATS,
     FOLLOW_PACKS,
     LIVE_STREAMS,
     NESTS,
@@ -334,6 +335,13 @@ val NavBarCatalog: Map<NavBarItem, NavBarItemDef> =
                 icon = MaterialSymbols.Group,
                 resolveRoute = { Route.Concords },
             ),
+        NavBarItem.GEOHASH_CHATS to
+            NavBarItemDef(
+                id = NavBarItem.GEOHASH_CHATS,
+                labelRes = R.string.location_channels,
+                icon = MaterialSymbols.LocationOn,
+                resolveRoute = { Route.NewGeohashChat },
+            ),
         NavBarItem.FOLLOW_PACKS to
             NavBarItemDef(
                 id = NavBarItem.FOLLOW_PACKS,
@@ -471,6 +479,7 @@ val BottomBarCategories: List<NavBarCategory> =
                 NavBarItem.PUBLIC_CHATS,
                 NavBarItem.RELAY_GROUPS,
                 NavBarItem.CONCORD,
+                NavBarItem.GEOHASH_CHATS,
             ),
         ),
         NavBarCategory(

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

@@ -156,6 +156,10 @@ private fun PreloadFor(
         // Covered by AccountFilterAssemblerSubscription (always-on).
         NavBarItem.NOTIFICATIONS -> Unit
 
+        // Anonymous location channels — the pinned avatar carries no metadata, and the cell's
+        // message subscription opens from the chat screen itself, so there's nothing to preload.
+        NavBarItem.GEOHASH_CHATS -> Unit
+
         // No relay feed to preload (loaded by the destination screen on demand).
         NavBarItem.PROFILE,
         NavBarItem.MY_LISTS,

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/settings/BottomBarSettingsScreen.kt

@@ -107,6 +107,7 @@ private val ExpandableItems =
         NavBarItem.PUBLIC_CHATS,
         NavBarItem.RELAY_GROUPS,
         NavBarItem.CONCORD,
+        NavBarItem.GEOHASH_CHATS,
     )
 
 /** Soft guidance, not a hard cap: a Material bottom bar reads best at ~5 tabs. */
@@ -588,6 +589,13 @@ private fun PickerChildren(
             GroupChildList(entries, pinnedKeys, accountViewModel, onTogglePin)
         }
 
+        NavBarItem.GEOHASH_CHATS -> {
+            val cells by accountViewModel.account.geohashList.flow
+                .collectAsStateWithLifecycle()
+            val entries = remember(cells) { cells.sorted().map { BottomBarEntry.Geohash(it) } }
+            GroupChildList(entries, pinnedKeys, accountViewModel, onTogglePin)
+        }
+
         else -> {}
     }
 }
@@ -828,6 +836,7 @@ private fun rememberPinnedVisual(
         is BottomBarEntry.PublicChat,
         is BottomBarEntry.RelayGroup,
         is BottomBarEntry.Concord,
+        is BottomBarEntry.Geohash,
         -> {
             // Read-only: the settings list resolves from cache; the live bar owns the subscription.
             val display = rememberGroupEntryDisplay(entry, accountViewModel, subscribe = false)

amethyst/src/main/res/values/strings.xml

@@ -962,6 +962,7 @@
     <string name="nip82_older_releases_hide">Hide older releases</string>
     <string name="shorts">Shorts</string>
     <string name="public_chats">Public Chats</string>
+    <string name="location_channels">Location Channels</string>
     <string name="follow_packs">Follow Packs</string>
     <string name="live_streams">Live Streams</string>
     <string name="nests">Nests</string>