⬆️ 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/obiutils/xopen.md

@@ -0,0 +1,38 @@
+# `obiutils` — Universal File I/O with Transparent Compression Support
+
+The `xopen`-based package in the `obiutils` module provides a unified interface for reading and writing files, streams, HTTP resources, or command outputs—**transparently handling multiple compression formats**: gzip, xz, zstd, and bzip2.
+
+## Key Functionalities
+
+- **`Ropen(f string)`**  
+  Opens a file, stdin (`"-"`), HTTP(S) URL, or shell command (e.g., `"|gzip -dc file.gz"`) for **buffered reading**, auto-detecting compression via magic bytes.
+
+- **`Wopen(f string)` / `WopenFile(...)`**  
+  Opens a file or stdout (`"-"`) for **buffered writing**, automatically compressing output based on extension (`.gz`, `.xz`, `.zst`, `.bz2`).
+
+- **Compression Detection**  
+  Functions like `IsGzip()`, `IsXz()`, `IsZst()`, and `IsBzip2()` inspect the first bytes of a buffered reader to infer format.
+
+- **Path Utilities**  
+  - `ExpandUser(path)` expands POSIX-style paths (`~`, `~/path`) to absolute ones.  
+  - `Exists(path)` checks file existence after user expansion.
+
+- **Error Handling**  
+  Defines semantic errors: `ErrNoContent`, `ErrDirNotSupported`.
+
+- **Buffered IO**  
+  All readers/writers use a default buffer size of `65,536` bytes for performance.
+
+- **Resource Management**  
+  `Close()` methods ensure proper cleanup of underlying readers/writers and compression streams.
+
+## Supported Sources & Formats
+
+| Source            | Format(s)              |
+|-------------------|------------------------|
+| Local files       | plain, `.gz`, `.xz`, `.zst`, `.bz2` |
+| Stdin (`"-"`)     | auto-detected          |
+| HTTP(S) URLs      | transparent decompression on stream read |
+| Pipe commands (`"|cmd"`) | output piped and auto-decompressed |
+
+This abstraction simplifies bioinformatics or data-processing pipelines where input sources vary widely, and compression is common.