soul loop-2: session events, conversation persistence, richer health + inbox

- soul.el: emit_session_start_event() logs structured InternalStateEvent on every boot; pre-serve snapshot saves boot-time graph mutations before any requests arrive
- routes.el: /health now returns boot count, node/edge counts, pulse; /api/sessions endpoint surfaces session-start history
- awareness.el: perceive() tries soul-inbox-pending then soul-inbox fallback, catches both tagging conventions
- chat.el: conv_history_persist/load provide cross-restart conversation continuity via engram

awareness.el

@@ -23,7 +23,19 @@ fn make_action(kind: String, payload: String) -> String {
 }
 
 fn perceive() -> String {
-    return engram_activate_json("soul-inbox-pending", 2)
+    // Try the primary inbox first
+    let from_pending: String = engram_activate_json("soul-inbox-pending", 2)
+    let pending_ok: Bool = !str_eq(from_pending, "") && !str_eq(from_pending, "[]")
+    if pending_ok {
+        return from_pending
+    }
+    // Fallback: broader inbox scan
+    let from_inbox: String = engram_activate_json("soul-inbox", 2)
+    let inbox_ok: Bool = !str_eq(from_inbox, "") && !str_eq(from_inbox, "[]")
+    if inbox_ok {
+        return from_inbox
+    }
+    return "[]"
 }
 
 fn attend(node_json: String) -> String {