api: add /api/neuron/memory/delete and /api/neuron/memory/update for UI memory CRUD

The UI needs full memory CRUD; the soul had create (handle_api_remember)
and the older /memory/forget + /memory/evolve, but no endpoints matching
the UI's delete/update contract.

POST /api/neuron/memory/delete {"id"}
  Hard delete. engram_forget is a true delete primitive (removes the node
  and all incident edges from the engram store), so no soft-delete
  fallback is needed. Unlike /memory/forget, this checks the node exists
  first - engram_forget silently no-ops on unknown ids, and a bad id must
  return an error, not fake success. Protected identity/values nodes are
  blocked, same as the other accumulation-path handlers.

POST /api/neuron/memory/update {"id","content"}
  Evolve-style update. The engram runtime has no in-place node mutation
  primitive (only node-create, strengthen, forget, connect), so update
  creates a new Memory node and wires a supersedes edge to the prior one,
  same pattern as handle_api_evolve_knowledge. Unlike /memory/evolve, id
  is required and must reference an existing node; create+link delegates
  to handle_api_evolve_memory. Returns {id, supersedes, ok}.

Both files syntax-checked with elc --target=c (exit 0, no stderr).
Compile-verified only - local builds cannot run the soul; needs Will's
build for runtime verification.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

routes.el

@@ -412,6 +412,12 @@ fn handle_request(method: String, path: String, body: String) -> String {
         if str_eq(clean, "/api/neuron/memory/forget") {
             return handle_api_forget(body)
         }
+        if str_eq(clean, "/api/neuron/memory/delete") {
+            return handle_api_memory_delete(body)
+        }
+        if str_eq(clean, "/api/neuron/memory/update") {
+            return handle_api_memory_update(body)
+        }
         if str_eq(clean, "/api/neuron/recall") {
             return handle_api_recall(method, path, body)
         }