value-graph 0.1.0: JSON-free, bigint-free binary snapshot layer

- src/snapshot.js: compact portable wire (VGST store / VGGP graph), binary maps for
  params/pattern/objects (no JSON), buffer values (no JS bigint), CRC-32 guarded.
- createFileStore: binary per-key files (encodeEntryBytes/decodeEntryBytes).
- ValueGraph snapshot/snapshotFile/restore/loadFile; keys base64url(params-bytes).
- 60 tests (node:test + rigor incl. 'flip ANY byte never decodes silently').

.gitignore

@@ -0,0 +1,4 @@
+node_modules/
+artifacts/
+*.log
+*.snap