feat: wire L3 write path via Embedder into router

Introduces Embedder contract in core:inference with a NoopEmbedder
default (zero vector) and wires both Embedder and L3MemoryStore into
DefaultRouterFacade. Each ChatTurnEvent emission now embeds the turn
content and writes a corresponding L3MemoryEntry, so cross-session
memory is captured at the source of truth (the event emission point).

InfrastructureModule defaults to NoopEmbedder + InMemoryL3MemoryStore
so the system runs without an external embedding model or vector store
wired. The TurboVec adapter stays unwired for now; switching to it is
a configuration concern (Epic 12 config layer).

Also gitignores apps/tui/logs/ (Kotlin TUI runtime logs, pre-Go rewrite).

.gitignore

@@ -74,3 +74,6 @@ correx-tui.log
 current.log
 # Go TUI build output
 apps/tui-go/bin/
+
+# TUI runtime logs (Kotlin TUI, pre-Go rewrite)
+apps/tui/logs/