⬆️ 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)

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@@ -0,0 +1,19 @@
+```markdown
+# DNA Scoring and Matching Utilities in `obialign`
+
+This module provides low-level utilities for computing nucleotide alignment scores using probabilistic and bit-encoded representations.
+
+- **Bit Encoding**: Nucleotides are encoded in 4-bit groups (e.g., `A=0b0001`, `C=0b0010`, etc.), enabling efficient bitwise comparison.
+- **`_MatchRatio(a, b)`**: Computes a normalized match ratio between two encoded bytes based on shared bits:
+  `ratio = common_bits / (bits_in_a × bits_in_b)`.
+- **`_FourBitsCount`**: Precomputed lookup table for Hamming weight (popcount) of 4-bit values.
+- **Log-space Arithmetic**: Helper functions (`_Logaddexp`, `_Logdiffexp`, `_Log1mexp`) ensure numerical stability in probabilistic computations.
+- **Phred-scaled Quality Integration**:
+  `_MatchScoreRatio(QF, QR)` derives log-odds match/mismatch scores from Phred quality values (`QF`, `QR`), modeling sequencing error probabilities.
+- **Precomputed Matrices**:
+  - `_NucPartMatch[i][j]`: Match ratios for all nucleotide pairs (from 4-bit codes).
+  - `_NucScorePartMatchMatch/Mismatch[i][j]`: Integer-scaled match/mismatch scores (×10) for quality pairs `(i, j)` in `[0..99]`.
+- **Thread-Safe Initialization**: `_InitDNAScoreMatrix()` ensures one-time, synchronized initialization of all scoring tables via a mutex.
+
+Designed for high-performance alignment kernels where speed and numerical robustness are critical.
+```