⬆️ 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/obiformats/fastseq_interface.md

@@ -0,0 +1,28 @@
+# `FormatHeader` Function Type in `obiformats`
+
+The `obiformats` package defines a core functional interface for sequence formatting within the OBITools4 ecosystem.
+
+- **Package**: `obiformats`  
+  Provides utilities for formatting biological sequences according to various output standards (e.g., FASTA, GenBank).
+
+- **Type Definition**:  
+  ```go
+  type FormatHeader func(sequence *obiseq.BioSequence) string
+  ```
+  - A `FormatHeader` is a *function type* that takes a pointer to an `obiseq.BioSequence` and returns its formatted header as a string.
+
+- **Semantic Role**:  
+  Encapsulates the logic for generating *header lines* (e.g., `>id description`) in sequence file formats.  
+  Decouples header formatting from core data structures (`BioSequence`), enabling modular and reusable format adapters.
+
+- **Usage Context**:  
+  - Used by writers/formatters to produce standardized headers when exporting sequences.  
+  - Allows custom header generation (e.g., for MIxS-compliant metadata, user-defined tags).  
+  - Supports polymorphism: different `FormatHeader` implementations can be swapped per output format.
+
+- **Dependencies**:  
+  - Relies on `obiseq.BioSequence`, the core sequence data model (ID, description, annotations, etc.).
+
+- **Design Intent**:  
+  Promotes clean separation of concerns: data (sequence) ↔ formatting logic.  
+  Facilitates extensibility for new output formats without modifying core types.