perf(talkie): fold idea board once, keep live via subscribeAll (#55)

IdeaReader folded eventStore.allEvents() on every activeIdeas()/capturedOf()
call — a full deserializing log scan per CHAT context build. Now folds once at
construction and stays current incrementally via subscribeAll(); the fold is
idempotent so seed/live overlap needs no dedupe.

core/talkie/src/main/kotlin/com/correx/core/talkie/IdeaReader.kt

@@ -1,46 +1,61 @@
 package com.correx.core.talkie
 
+import com.correx.core.events.events.EventPayload
 import com.correx.core.events.events.IdeaCapturedEvent
 import com.correx.core.events.events.IdeaDiscardedEvent
 import com.correx.core.events.events.IdeaPromotedEvent
 import com.correx.core.events.stores.EventStore
 import com.correx.core.events.types.SessionId
 import com.correx.core.talkie.model.Idea
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.launch
+import java.util.concurrent.ConcurrentHashMap
 
 /**
- * Rebuilds the operator's idea board from the event log. Cross-session by design: it folds over
- * [EventStore.allEvents] rather than a single session's replay, so an idea captured in one session
- * shows on the board (and feeds the router) in every session. A captured idea is dropped once a
- * matching [IdeaDiscardedEvent] (or [IdeaPromotedEvent]) tombstones it (invariant #1 — the capture
- * stays in the log).
+ * Holds the operator's idea board in memory. Cross-session by design: it folds over the whole event
+ * log (not a single session's replay), so an idea captured in one session shows on the board (and
+ * feeds the router) in every session. A captured idea is dropped once a matching [IdeaDiscardedEvent]
+ * (or [IdeaPromotedEvent]) tombstones it (invariant #1 — the capture stays in the log).
+ *
+ * The board is folded ONCE at construction from [EventStore.allEvents] (a full, eager table load) and
+ * then kept current incrementally via [EventStore.subscribeAll]. This replaces the previous
+ * fold-the-entire-log-per-call design, which ran a full deserializing scan on every CHAT context
+ * build. The fold is idempotent (map put / set add), so the seed⇄live overlap needs no dedupe.
  */
-class IdeaReader(private val eventStore: EventStore) {
+class IdeaReader(
+    eventStore: EventStore,
+    scope: CoroutineScope = CoroutineScope(Dispatchers.Default + SupervisorJob()),
+) {
+    // id -> its capture event (source for text/sessionId); tombstoned = discarded/promoted ids.
+    private val captures = ConcurrentHashMap<String, IdeaCapturedEvent>()
+    private val tombstoned: MutableSet<String> = ConcurrentHashMap.newKeySet()
 
-    /** Active ideas (captured, not later discarded or promoted) across all sessions, newest first. */
-    fun activeIdeas(): List<Idea> {
-        val tombstoned = mutableSetOf<String>()
-        val captured = mutableListOf<Idea>()
-        eventStore.allEvents().forEach { stored ->
-            when (val payload = stored.payload) {
+    init {
+        eventStore.allEvents().forEach { apply(it.payload) }
+        scope.launch { eventStore.subscribeAll().collect { apply(it.payload) } }
+    }
+
+    private fun apply(payload: EventPayload) {
+        when (payload) {
             is IdeaDiscardedEvent -> tombstoned += payload.ideaId
             is IdeaPromotedEvent -> tombstoned += payload.ideaId
-                is IdeaCapturedEvent -> captured += Idea(payload.ideaId, payload.text, payload.timestampMs)
+            is IdeaCapturedEvent -> captures[payload.ideaId] = payload
             else -> Unit
         }
     }
-        return captured.filterNot { it.id in tombstoned }.sortedByDescending { it.capturedAtMs }
-    }
+
+    /** Active ideas (captured, not later discarded or promoted) across all sessions, newest first. */
+    fun activeIdeas(): List<Idea> =
+        captures.values
+            .filterNot { it.ideaId in tombstoned }
+            .map { Idea(it.ideaId, it.text, it.timestampMs) }
+            .sortedByDescending { it.capturedAtMs }
 
     /** The session that captured [ideaId], so a tombstone lands alongside its capture. */
-    fun sessionOf(ideaId: String): SessionId? =
-        capturedOf(ideaId)?.sessionId
+    fun sessionOf(ideaId: String): SessionId? = captures[ideaId]?.sessionId
 
     /** The captured text of [ideaId] (so a promotion can write it into the project profile), or null. */
-    fun textOf(ideaId: String): String? =
-        capturedOf(ideaId)?.text
-
-    private fun capturedOf(ideaId: String): IdeaCapturedEvent? =
-        eventStore.allEvents()
-            .mapNotNull { it.payload as? IdeaCapturedEvent }
-            .firstOrNull { it.ideaId == ideaId }
+    fun textOf(ideaId: String): String? = captures[ideaId]?.text
 }