⬆️ 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_test.md

@@ -0,0 +1,19 @@
+# `obiutils` Package: Semantic Overview
+
+The `xopen.go` test suite (via GoCheck) validates utility functions for flexible file/stream I/O in Go. Key features:
+
+- **`IsGzip()`**: Detects gzip compression by inspecting the first two bytes (`0x1f 0x8b`) of a `bufio.Reader`.
+- **`Ropen()`**: Unified reader opener supporting:
+  - Local files (plain or `.gz`)
+  - Standard input (`"-"`) — *note: currently unimplemented in tests*
+  - HTTP(S) URLs (via `net/http`)
+- **`Wopen()`**: Unified writer opener for:
+  - Local files (`".gz"` triggers gzip compression)
+  - Standard output via `"-"`
+- **`Exists()`**: Checks file/directory existence (supports `~` expansion).
+- **`ExpandUser()`**: Expands shell-like paths (`~/...`) to absolute ones.
+- **Tested robustness**:
+  - Handles missing files, invalid URLs (404), and malformed paths.
+  - Validates gzip detection accuracy on both plain and compressed data.
+
+All operations abstract away compression/format details, enabling uniform read/write semantics across local files, pipes (commented out), and remote HTTP resources.