⬆️ 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/obikmer/encodefourmer.md

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+# Semantic Description of `obikmer` Package
+
+The `obikmer` package provides efficient k-mer encoding and comparison utilities for biological sequences, optimized for DNA analysis.
+
+## Core Functionalities
+
+1. **Nucleotide Encoding**  
+   - `EncodeNucleotide(b byte)`: Maps DNA bases (A, C, G, T/U) to 2-bit values:  
+     `0→A`, `1→C`, `2→G`, `3→T/U`.  
+     Ambiguous or non-standard characters (e.g., N, R, Y) default to `A` (`0`).  
+     Uses a lookup table for O(1) performance.
+
+2. **4-mer Encoding**  
+   - `Encode4mer(seq, buffer)`: Converts a biological sequence into overlapping 4-mers.  
+     Each k-mer is encoded as an unsigned byte (0–255), where each nucleotide contributes 2 bits.  
+     Supports optional buffer reuse for memory efficiency.
+
+3. **4-mer Indexing**  
+   - `Index4mer(seq, index, buffer)`: Builds an inverted index mapping each 4-mer code (0–255) to all its occurrence positions in the sequence.  
+     Returns `[][]int`, where rows correspond to k-mer codes and columns list positions.
+
+4. **Fast Sequence Comparison**  
+   - `FastShiftFourMer(...)`: Compares two sequences using a FASTA-like shift-scoring algorithm.  
+     - Uses precomputed 4-mer index of a reference sequence and encodes the query.  
+     - Counts co-occurring 4-mers across all possible shifts (`refpos − queryPos`).  
+     - Computes raw and relative scores (normalized by alignment length).  
+     - Returns optimal shift, count of matching 4-mers, and maximum score (raw or relative).
+
+## Design Highlights
+
+- **Memory-aware**: Supports buffer reuse to minimize allocations.  
+- **Robustness**: Non-canonical bases handled gracefully (defaulting to A).  
+- **Performance-oriented**: O(n) encoding and indexing; efficient hash-based shift counting.  
+
+Intended for rapid alignment-free sequence comparison in metabarcoding or metagenomic workflows.