remove :message-store-api and migrate functionality to :journal-api and :reflection-api

- Removed `:message-store-api` module and associated classes (ConversationStore, ReflectionStore, Ids, etc.).
- Migrated reusable components to `:journal-api` (conversation-related) and `:reflection-api` (reflection-related).
- Updated imports and module dependencies across all projects to reflect new structure.
- Adjusted build scripts and tests for compatibility with the new APIs.

agent-toolsets/build.gradle.kts

@@ -21,7 +21,8 @@ kotlin {
 
     sourceSets {
         commonMain.dependencies {
-            api(project(":message-store-api"))
+            api(project(":journal-api"))
+            api(project(":reflection-api"))
             api(project(":context-api"))
 
             // litert-kmp: LiteTool интерфейс (sync describe/invoke)