perf: index git status events and observe repo event reactively

Audit follow-up on the Git Repository screen.

- Add GitStatusIndex, a process-level Map<targetId, latest GitStatusEvent>
  fed by an initial scan on Dispatchers.IO and incrementally maintained
  from LocalCache.live.newEventBundles. GitStatusPill now does an O(1)
  map lookup instead of scanning the entire LocalCache on every issue/
  patch row at composition time on the main thread.

- Observe the GitRepositoryEvent reactively in the screen via
  observeNoteEvent so the title and Overview tab refresh when the event
  arrives after composition or when the maintainer publishes a new
  version.

amethyst/src/main/java/com/vitorpamplona/amethyst/model/GitStatusIndex.kt

@@ -0,0 +1,82 @@
+/*
+ * Copyright (c) 2025 Vitor Pamplona
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to use,
+ * copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the
+ * Software, and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+ * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+ * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+package com.vitorpamplona.amethyst.model
+
+import com.vitorpamplona.quartz.nip01Core.core.HexKey
+import com.vitorpamplona.quartz.nip34Git.status.GitStatusEvent
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
+import java.util.concurrent.atomic.AtomicBoolean
+
+/**
+ * Cross-screen index of the most recent NIP-34 status event (kinds
+ * 1630-1633) per target id, kept up to date from
+ * [LocalCache.live.newEventBundles]. Status events are not tracked in
+ * `Note.replies` (see `LocalCache.computeReplyTo`), so the only way to
+ * find them otherwise would be a full cache scan per row.
+ */
+object GitStatusIndex {
+    private val scope = CoroutineScope(Dispatchers.IO + SupervisorJob())
+    private val started = AtomicBoolean(false)
+
+    private val mutableLatestByTarget = MutableStateFlow<Map<HexKey, GitStatusEvent>>(emptyMap())
+    val latestByTarget: StateFlow<Map<HexKey, GitStatusEvent>> = mutableLatestByTarget.asStateFlow()
+
+    fun startIfNeeded() {
+        if (!started.compareAndSet(false, true)) return
+        scope.launch {
+            val initial = HashMap<HexKey, GitStatusEvent>()
+            LocalCache.notes.forEach { _, note ->
+                val event = note.event as? GitStatusEvent ?: return@forEach
+                val target = event.rootEventId() ?: return@forEach
+                val current = initial[target]
+                if (current == null || event.createdAt > current.createdAt) {
+                    initial[target] = event
+                }
+            }
+            mutableLatestByTarget.value = initial
+
+            LocalCache.live.newEventBundles.collect { bundle ->
+                processBundle(bundle)
+            }
+        }
+    }
+
+    private fun processBundle(bundle: Set<Note>) {
+        var modified: HashMap<HexKey, GitStatusEvent>? = null
+        for (note in bundle) {
+            val event = note.event as? GitStatusEvent ?: continue
+            val target = event.rootEventId() ?: continue
+            val map = modified ?: mutableLatestByTarget.value
+            val current = map[target]
+            if (current == null || event.createdAt > current.createdAt) {
+                if (modified == null) modified = HashMap(mutableLatestByTarget.value)
+                modified[target] = event
+            }
+        }
+        modified?.let { mutableLatestByTarget.value = it }
+    }
+}

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

@@ -30,21 +30,21 @@ import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.derivedStateOf
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
-import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.unit.dp
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.commons.icons.symbols.Icon
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbol
 import com.vitorpamplona.amethyst.commons.icons.symbols.MaterialSymbols
-import com.vitorpamplona.amethyst.model.LocalCache
+import com.vitorpamplona.amethyst.model.GitStatusIndex
 import com.vitorpamplona.amethyst.ui.stringRes
 import com.vitorpamplona.quartz.nip34Git.status.GitStatusAppliedEvent
 import com.vitorpamplona.quartz.nip34Git.status.GitStatusClosedEvent
@@ -72,38 +72,9 @@ private fun GitStatusEvent.statusKind(): StatusKind =
 
 @Composable
 fun rememberLatestStatus(targetIdHex: String): GitStatusEvent? {
-    var status by remember(targetIdHex) {
-        mutableStateOf(scanForLatestStatus(targetIdHex))
-    }
-
-    LaunchedEffect(targetIdHex) {
-        LocalCache.live.newEventBundles.collect { bundle ->
-            for (note in bundle) {
-                val event = note.event as? GitStatusEvent ?: continue
-                if (event.rootEventId() == targetIdHex) {
-                    val current = status
-                    if (current == null || event.createdAt > current.createdAt) {
-                        status = event
-                    }
-                }
-            }
-        }
-    }
-
-    return status
-}
-
-private fun scanForLatestStatus(targetIdHex: String): GitStatusEvent? {
-    var latest: GitStatusEvent? = null
-    LocalCache.notes.forEach { _, note ->
-        val event = note.event
-        if (event is GitStatusEvent && event.rootEventId() == targetIdHex) {
-            val current = latest
-            if (current == null || event.createdAt > current.createdAt) {
-                latest = event
-            }
-        }
-    }
+    LaunchedEffect(Unit) { GitStatusIndex.startIfNeeded() }
+    val index by GitStatusIndex.latestByTarget.collectAsStateWithLifecycle()
+    val latest by remember(targetIdHex) { derivedStateOf { index[targetIdHex] } }
     return latest
 }
 

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

@@ -35,6 +35,7 @@ import androidx.compose.material3.SecondaryTabRow
 import androidx.compose.material3.Tab
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
 import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
@@ -44,6 +45,7 @@ import androidx.compose.ui.unit.dp
 import androidx.lifecycle.viewmodel.compose.viewModel
 import com.vitorpamplona.amethyst.R
 import com.vitorpamplona.amethyst.model.AddressableNote
+import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNoteEvent
 import com.vitorpamplona.amethyst.ui.feeds.WatchLifecycleAndUpdateModel
 import com.vitorpamplona.amethyst.ui.feeds.rememberForeverPagerState
 import com.vitorpamplona.amethyst.ui.layouts.DisappearingScaffold
@@ -120,6 +122,7 @@ private fun GitRepositoryScreen(
     WatchLifecycleAndUpdateModel(patchesViewModel)
     RepositoryFilterAssemblerSubscription(note, accountViewModel.dataSources().gitRepository)
 
+    val event by observeNoteEvent<GitRepositoryEvent>(note, accountViewModel)
     val pagerState = rememberForeverPagerState(note.idHex + "GitRepoScreenPagerState") { 3 }
 
     DisappearingScaffold(
@@ -128,7 +131,7 @@ private fun GitRepositoryScreen(
             Column {
                 ShorterTopAppBar(
                     title = {
-                        TopBarTitle(note)
+                        TopBarTitle(event = event, fallback = note.dTag())
                     },
                     navigationIcon = {
                         Row(TitleIconModifier, verticalAlignment = Alignment.CenterVertically) {
@@ -170,9 +173,9 @@ private fun GitRepositoryScreen(
         ) { page ->
             when (page) {
                 0 -> {
-                    val event = note.event as? GitRepositoryEvent
-                    if (event != null) {
-                        GitRepositoryOverview(event, accountViewModel, nav)
+                    val currentEvent = event
+                    if (currentEvent != null) {
+                        GitRepositoryOverview(currentEvent, accountViewModel, nav)
                     } else {
                         EmptyMessage(stringRes(R.string.loading_feed))
                     }
@@ -201,11 +204,12 @@ private fun GitRepositoryScreen(
 }
 
 @Composable
-private fun TopBarTitle(note: AddressableNote) {
-    val event = note.event as? GitRepositoryEvent
-    val title = event?.name() ?: note.dTag()
+private fun TopBarTitle(
+    event: GitRepositoryEvent?,
+    fallback: String,
+) {
     Text(
-        text = title,
+        text = event?.name() ?: fallback,
         style = MaterialTheme.typography.titleMedium,
         fontWeight = FontWeight.SemiBold,
         maxLines = 1,