⬆️ version bump to v4.5

- Update obioptions.Version from "Release 4.4.29" to "/v/ Release v5"
- Update version.txt from 4.29 → .30
(automated by Makefile)

autodoc/docmd/pkg/obilua/mutex.md

@@ -0,0 +1,30 @@
+# `obilua.Mutex`: Thread-Safe Synchronization in Lua via Go's sync.Mutex
+
+This package exposes **Go’s `sync.Mutex`** to the Lua environment using [gopher-lua](https://github.com/yuin/gopher-lua), enabling safe concurrent access from Lua scripts.
+
+## Key Features
+
+- **Custom userdata type**: Registers a new metatable `"Mutex"` in the Lua state.
+- **Constructor function**:
+  - ` Mutex.new() → mutex userdata`  
+    Creates and returns a new Go-backed mutex instance.
+- **Instance methods**:
+  - `mutex:lock()` — Acquires the lock (blocks until available).
+  - `mutex:unlock()` — Releases the lock.
+- **Type safety**: Validates that only valid mutex userdatas are passed to `lock`/`unlock`.
+- **Integration**: Designed for embedding Lua in Go applications requiring synchronization (e.g., multi-threaded scripting).
+
+## Usage Example
+
+```lua
+local m = Mutex.new()
+m:lock()   -- Acquire lock (safe across goroutines)
+-- critical section
+m:unlock()
+```
+
+## Implementation Notes
+
+- Mutex state is stored in a Go `*sync.Mutex` inside Lua userdata.
+- No reference counting or finalizers — user must manually manage lock/unlock lifecycle to avoid deadlocks.
+- Thread-safe *from Go side only*; Lua calls must respect goroutine safety (e.g., avoid calling from multiple VMs concurrently).