feat(neuron): rung-zero live - first conversation on pure-Neuron stack

- kernel/graph: nodes+edges append-only store
- conversation: chained turns, memory node, fold-based reads
- session/sessions: durable admission inbox, promotion, serialized runner,
  eager tool settlement, provider/dialect/transform injected at composition
- provider/dialects: raw-wire anthropic + openai-compatible, registry
- llm/stream, tools(bash/read/write), auth(local claims), boot composition
- providers resolve from ~/.config/neuron/providers.json - no baked vendors

nix/node_modules.nix

@@ -10,7 +10,7 @@
     ]).nodeModules.${stdenvNoCC.hostPlatform.system},
 }:
 let
-  packageJson = lib.pipe ../packages/opencode/package.json [
+  packageJson = lib.pipe ../packages/neuron/package.json [
     builtins.readFile
     builtins.fromJSON
   ];