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

chat.el

@@ -123,6 +123,33 @@ fn clean_llm_response(s: String) -> String {
     return s3
 }
 
+// conv_history_persist — save conversation history to engram for cross-restart continuity.
+// Stores as a Conversation node. Overwrites by using consistent label "conv:history".
+fn conv_history_persist(hist: String) -> Void {
+    if str_eq(hist, "") { return "" }
+    if str_eq(hist, "[]") { return "" }
+    let ts: Int = time_now()
+    let tags: String = "[\"conv-history\",\"persistent\"]"
+    let discard: String = engram_node_full(
+        hist, "Conversation", "conv:history",
+        el_from_float(0.7), el_from_float(0.8), el_from_float(0.9),
+        "Episodic", tags
+    )
+}
+
+// conv_history_load — restore conversation history from engram on first access.
+// Returns the most recent "conv:history" node content, or "" if none found.
+fn conv_history_load() -> String {
+    let results: String = engram_search_json("conv:history", 3)
+    if str_eq(results, "") { return "" }
+    if str_eq(results, "[]") { return "" }
+    let node: String = json_array_get(results, 0)
+    let content: String = json_get(node, "content")
+    // Validate it looks like a JSON array
+    if !str_starts_with(content, "[") { return "" }
+    return content
+}
+
 fn handle_chat(body: String) -> String {
     let message: String = json_get(body, "message")
     if str_eq(message, "") {
@@ -132,7 +159,9 @@ fn handle_chat(body: String) -> String {
     let ctx: String = engram_compile(message)
     let system: String = build_system_prompt(ctx)
 
-    let stored_hist: String = state_get("conv_history")
+    // Load from state; if empty, try to recover from engram (cross-restart continuity)
+    let state_hist: String = state_get("conv_history")
+    let stored_hist: String = if str_eq(state_hist, "") { conv_history_load() } else { state_hist }
     let hist_len: Int = if str_eq(stored_hist, "") { 0 } else { json_array_len(stored_hist) }
     let full_system: String = if hist_len > 0 {
         system + "\n\n[RECENT CONVERSATION — last " + int_to_str(hist_len) + " turns]\n" + stored_hist
@@ -163,6 +192,7 @@ fn handle_chat(body: String) -> String {
         updated_hist2
     }
     state_set("conv_history", final_hist)
+    conv_history_persist(final_hist)
 
     let activation_nodes: String = engram_activate_json(message, 2)
     let act_ok: Bool = !str_eq(activation_nodes, "") && !str_eq(activation_nodes, "[]")