feat(client): client-side caching for conversation list via agent.outbox events

Adds `agent.conversationStore` (read-only view on `conversation` table) to
the :proto Agent interface, plus `agent.renameConversation(id, title?)`
command. Client-side cache in :client is built from a snapshot
(`remote.listFlow(0)` → `local.upsert(...)`) + live updates via
`outbox.agentEvents()` (Created/Deleted/Renamed/Touched).

Changes:
- :journal-api — split `ConversationStore` (read-only: get/list) and
  `MutableConversationStore` (CRUD: upsert/delete/rename/touch);
  `ConversationStore` gained `listFlow` (cold-flow paging via `list`).
- :outbox-api — `AgentEvent.Touched(date, id, updatedAt)` event so
  client cache stays fresh after `send()` (which bumps `updatedAt`).
- :proto.Agent — added `conversationStore: ConversationStore` property,
  added `renameConversation(id, title?): Instant?` command, removed
  `getConversations(offset, limit)` (now: `conversationStore.list(...)`).
- :server — `GET /conversations` now returns `List<ConversationRecord>`
  (lightweight metadata, no handle/image-support flags); `PATCH
  /conversations/{id}` uses `agent.renameConversation` and returns
  the updated `ConversationRecord`.
- :journal-inmemory — expanded targets to jvm+macos+linux+mingw (matches
  :client); moved `InMemoryMutableConversationStore` here from
  :storage-inmemory so :client can use it without pulling ios targets.
- :storage-inmemory — depends on :journal-inmemory.
- :storage-ksqlite — pre-staged rename `KsqliteConversationStore` →
  `KsqliteMutableConversationStore` to match the new interface split.
- :standalone — `ChatAgent` exposes `conversationStore` as a read-only
  view of its `mutableConversationStore`; emits `AgentEvent.Touched`
  after each `send()` (after `conversationStore.touch(id, ts)`).
- :client — new `HttpConversationStore` (read-only HTTP impl);
  `AgentikAgent` wraps the agent with `wrapWithLocalConversationCache`
  so the client sees an in-memory cache (snapshot + outbox events)
  instead of direct HTTP. Cache scope + HttpClient + background job
  all cancelled in `agent.close()`.
- :client/README — new «Кэш списка бесед» section with the
  `listFlow → upsert` / `agentEvents → apply` pattern and a note that
  `conversationStore` is read-only (writes only via Agent commands).

All 96 jvmTest tasks green.

agentik-tui/src/commonTest/kotlin/pw/binom/agentik/tui/FakeAgent.kt

@@ -3,6 +3,7 @@ package pw.binom.agentik.tui
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableSharedFlow
 import kotlinx.coroutines.flow.emptyFlow
+import pw.binom.agentik.journal.ConversationStore
 import pw.binom.agentik.journal.JournalStore
 import pw.binom.agentik.outbox.OutboxStore
 import pw.binom.agentik.proto.Agent
@@ -32,9 +33,12 @@ internal class FakeAgent(
     override val journal: JournalStore = error("journal not used in TuiBackend tests")
     override val outbox: OutboxStore = object : OutboxStore {
         override fun events(after: Instant?) = emptyFlow<pw.binom.agentik.outbox.CommonEvent>()
+        override fun agentEvents(after: Instant?) = emptyFlow<pw.binom.agentik.outbox.CommonEvent.Agent>()
+        override fun conversationEvents(after: Instant?, conversationId: String?) = emptyFlow<pw.binom.agentik.outbox.CommonEvent.Conversation>()
         override suspend fun earliestEventDate(): Instant = Instant.DISTANT_PAST
         override fun close() {}
     }
+    override val conversationStore: ConversationStore = error("conversationStore not used in TuiBackend tests")
 
     override fun createConversation(temp: Boolean): Conversation {
         createCount++
@@ -49,8 +53,7 @@ internal class FakeAgent(
     override suspend fun deleteConversation(id: String): Boolean =
         conversations.removeAll { it.id == id }
 
-    override suspend fun getConversations(offset: Int, limit: Int): List<Conversation> =
-        conversations.toList()
+    override suspend fun renameConversation(id: String, title: String?): Instant? = null
 }
 
 /**