feat(soul): add sessions layer, MCP connectors, conversation continuity fix

- sessions.el: new sessions module with session management and approval gate
- routes.el: wire /api/sessions routes (list, get, create, approve, tool_result)
- chat.el: thread-aware activation — short messages anchor to last reply
  before engram compilation so follow-ups stay on-topic
- chat.el: agentic path tracks per-session history (session_hist_{id})
  instead of shared conv_history, seeding each turn with prior context
- chat.el: add call_neuron_mcp, dispatch_tool, is_builtin_tool, next_bridge_id
  agentic_loop, bridge_save, agentic_resume, handle_tool_result
- dist/soul: rebuild with all of the above

dist/memory.elh

@@ -11,3 +11,6 @@ extern fn mem_forget(node_id: String) -> Void
 extern fn mem_consolidate() -> String
 extern fn mem_save(path: String) -> Void
 extern fn mem_load(path: String) -> Void
+extern fn mem_boot_count_get() -> Int
+extern fn mem_boot_count_inc() -> Int
+extern fn mem_emit_state_event(trigger: String, kind: String, content: String) -> String