feat(nvim-core): implement bidirectional event streaming and real-time shadow buffer

- Created global thread-safe NvimState to shadow Neovim context.
- Injected Lua autocmds (CursorMoved, TextChanged) on connection to stream events back to MCP.
- Upgraded msgpack RPC loop to intercept and parse 'mcp_event' notifications alongside standard responses.
- Optimized nvim_get_cursor to pull instantly from the local shadow buffer, bypassing RPC round-trips.

Cargo.lock

@@ -497,6 +497,20 @@ dependencies = [
  "syn 3.0.6",
 ]
 
+[[package]]
+name = "dashmap"
+version = "6.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e6361d5c062261c78a176addb82d4c821ae42bed6089de0e12603cd25de2059c"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+ "hashbrown 0.14.5",
+ "lock_api",
+ "once_cell",
+ "parking_lot_core",
+]
+
 [[package]]
 name = "data-encoding"
 version = "2.11.1"
@@ -807,6 +821,12 @@ dependencies = [
  "rand_core 0.10.1",
 ]
 
+[[package]]
+name = "hashbrown"
+version = "0.14.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e5274423e17b7c9fc20b6e7e208532f9b19825d82dfd615708b70edd83df41f1"
+
 [[package]]
 name = "hashbrown"
 version = "0.16.1"
@@ -1375,6 +1395,8 @@ dependencies = [
 name = "nvim-core"
 version = "0.1.0"
 dependencies = [
+ "bytes",
+ "dashmap",
  "dirs",
  "mcp-stdio",
  "rmcp",