perf(observeEdits): filter modification updates at the flow level

`observeEdits` in NoteCompose previously listened to the raw
`note.flow().edits.stateFlow` and re-ran `findModificationEventsForNote`
(an IO scan) inside a `LaunchedEffect` on every emission — even when
the emission didn't change the actual list of modifications. That
mutated `editState` repeatedly with the same value during scroll on
any active TextNote.

Add `observeNoteModifications` in EventObservers.kt: it does the IO
resolution via `mapLatest { LocalCache.findLatestModificationForNote(note) }`
on Dispatchers.IO, then `distinctUntilChanged()` — so the State only
updates (and the consumer's LaunchedEffect only re-keys) when the
modification list truly changes. The State is `null` until the first
IO resolution completes; consumers treat that as "still loading" and
don't flip the UI to "no edits" prematurely.

Drop the now-unused `observeNoteEdits` and the
`AccountViewModel.findModificationEventsForNote` wrapper.

amethyst/src/main/java/com/vitorpamplona/amethyst/service/relayClient/reqCommand/event/EventObservers.kt

@@ -22,8 +22,10 @@ package com.vitorpamplona.amethyst.service.relayClient.reqCommand.event
 
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.State
+import androidx.compose.runtime.produceState
 import androidx.compose.runtime.remember
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import com.vitorpamplona.amethyst.model.LocalCache
 import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.model.NoteState
 import com.vitorpamplona.amethyst.model.User
@@ -359,17 +361,29 @@ fun observeNoteOts(
     return flow.collectAsStateWithLifecycle()
 }
 
+// Resolves the actual modification list off the main thread and filters identical results,
+// so the caller's LaunchedEffect only fires when the list of edits truly changes.
+// Returns `null` until the first IO resolution completes — callers should treat that as
+// "still loading" and not flip their UI to "no edits".
+@OptIn(ExperimentalCoroutinesApi::class)
 @Composable
-fun observeNoteEdits(
+fun observeNoteModifications(
     note: Note,
     accountViewModel: AccountViewModel,
-): State<NoteState?> {
+): State<List<Note>?> {
     // Subscribe in the relay for changes in this note.
     EventFinderFilterAssemblerSubscription(note, accountViewModel)
 
-    // Subscribe in the LocalCache for changes that arrive in the device
-    val flow = remember(note) { note.flow().edits.stateFlow }
-    return flow.collectAsStateWithLifecycle()
+    return produceState<List<Note>?>(initialValue = null, note) {
+        note
+            .flow()
+            .edits
+            .stateFlow
+            .mapLatest { LocalCache.findLatestModificationForNote(note) }
+            .distinctUntilChanged()
+            .flowOn(Dispatchers.IO)
+            .collect { value = it }
+    }
 }
 
 @Composable

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/note/NoteCompose.kt

@@ -66,8 +66,8 @@ import com.vitorpamplona.amethyst.model.LocalCache
 import com.vitorpamplona.amethyst.model.Note
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.channel.observeChannelPicture
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeCommunityApprovalNeedStatus
-import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNoteEdits
 import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNoteEvent
+import com.vitorpamplona.amethyst.service.relayClient.reqCommand.event.observeNoteModifications
 import com.vitorpamplona.amethyst.ui.components.ClickableBox
 import com.vitorpamplona.amethyst.ui.components.GenericLoadable
 import com.vitorpamplona.amethyst.ui.components.RobohashFallbackAsyncImage
@@ -1783,23 +1783,25 @@ fun observeEdits(
             )
         }
 
-    val updatedNote by observeNoteEdits(baseNote, accountViewModel)
+    // Upstream resolves on IO and `distinctUntilChanged`s, so this LaunchedEffect only
+    // fires when the actual modification list changes — no more recomputing + reassigning
+    // editState on every unrelated emission of the edits flow.
+    val modifications by observeNoteModifications(baseNote, accountViewModel)
 
-    LaunchedEffect(key1 = updatedNote) {
-        updatedNote?.note?.let {
-            val newModifications = accountViewModel.findModificationEventsForNote(it)
-            if (newModifications.isEmpty()) {
-                if (editState.value !is GenericLoadable.Empty) {
-                    editState.value = GenericLoadable.Empty()
-                }
+    LaunchedEffect(modifications) {
+        val mods = modifications ?: return@LaunchedEffect
+        if (mods.isEmpty()) {
+            if (editState.value !is GenericLoadable.Empty) {
+                editState.value = GenericLoadable.Empty()
+            }
+        } else {
+            val current = editState.value
+            if (current is GenericLoadable.Loaded) {
+                current.loaded.updateModifications(mods)
             } else {
-                if (editState.value is GenericLoadable.Loaded) {
-                    (editState.value as? GenericLoadable.Loaded<EditState>)?.loaded?.updateModifications(newModifications)
-                } else {
-                    val state = EditState()
-                    state.updateModifications(newModifications)
-                    editState.value = GenericLoadable.Loaded(state)
-                }
+                val state = EditState()
+                state.updateModifications(mods)
+                editState.value = GenericLoadable.Loaded(state)
             }
         }
     }

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

@@ -1310,11 +1310,6 @@ class AccountViewModel(
 
     fun cachedModificationEventsForNote(note: Note) = LocalCache.cachedModificationEventsForNote(note)
 
-    suspend fun findModificationEventsForNote(note: Note): List<Note> =
-        withContext(Dispatchers.IO) {
-            LocalCache.findLatestModificationForNote(note)
-        }
-
     fun checkGetOrCreatePublicChatChannel(key: HexKey): PublicChatChannel = LocalCache.getOrCreatePublicChatChannel(key)
 
     fun checkGetOrCreateLiveActivityChannel(key: Address): LiveActivitiesChannel = LocalCache.getOrCreateLiveChannel(key)