rename crates/ to engrams/, bindings/ to receptors/

- crates/ → engrams/ (Rust engrams live here)
- bindings/ → receptors/ (cross-language access points into the graph)
- Cargo.toml workspace paths updated

engram/receptors/go/README.md

@@ -0,0 +1,25 @@
+# Go Bindings (planned v0.2)
+
+Engram-core will be exposed to Go via CGo and the `engram-ffi` shared library.
+
+```go
+// #cgo LDFLAGS: -L../../target/release -lengram_ffi
+// #include "engram.h"
+import "C"
+import "unsafe"
+
+func Open(path string) *EngramDb {
+    cpath := C.CString(path)
+    defer C.free(unsafe.Pointer(cpath))
+    handle := C.engram_open(cpath)
+    if handle == nil {
+        return nil
+    }
+    return &EngramDb{handle: handle}
+}
+```
+
+## Status
+
+Stub only. The header file (`engram.h`) will be generated by `cbindgen` in v0.2.
+Full idiomatic Go wrapper with context support and error returns planned.