⬆️ 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/obialign/alignment.md

@@ -0,0 +1,22 @@
+# `obialign` Package: Sequence Alignment Utilities
+
+The `obialign` package provides core functions for pairwise biological sequence alignment in Go, designed to work with `obiseq.BioSequence` objects.
+
+- **Core Alignment Construction**: `_BuildAlignment()` and `BuildAlignment()` reconstruct aligned sequences from a precomputed alignment path (e.g., output by dynamic programming). It supports gap characters and reuses buffers for efficiency.
+
+- **Quality-Aware Consensus Building**: `BuildQualityConsensus()` generates a consensus sequence from an alignment and per-base quality scores:
+  - At mismatches, it retains the higher-quality base.
+  - When qualities are equal and bases differ, an IUPAC ambiguity code is used (via `_FourBitsBaseCode`/`_Decode`).
+  - Quality values are combined and adjusted for mismatches using a Phred-like error probability model.
+  - Optionally records mismatch statistics in sequence attributes.
+
+- **Performance & Memory Efficiency**: Uses preallocated buffers (via `PEAlignArena`) or fallback allocation, with slice recycling to minimize GC pressure.
+
+- **Metadata Handling**: Preserves sequence IDs and definitions in output; supports optional mismatch reporting for downstream analysis.
+
+- **Alignment Path Format**: The path is a sequence of signed integers encoding:
+  - Negative steps → deletions in seqB (insertion in A),
+  - Positive steps → insertions in B,
+  - Consecutive pairs encode match/mismatch runs.
+
+This package is part of the OBITools4 ecosystem, targeting high-throughput amplicon or metagenomic data processing.