⬆️ 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/obiiter/limitmemory.md

@@ -0,0 +1,29 @@
+# Memory-Limited Biosequence Iterator
+
+This Go function extends an `IBioSequence` iterator with memory-aware throttling to prevent excessive heap allocation during data processing.
+
+## Core Functionality
+
+- **`LimitMemory(fraction float64)`**  
+  Returns a new iterator that respects an upper bound on heap usage relative to total system memory.
+
+- **Memory Monitoring**  
+  Uses `runtime.ReadMemStats()` and `github.com/pbnjay/memory.TotalMemory()` to compute the current heap fraction (`Alloc / TotalMemory`) dynamically.
+
+- **Backpressure Mechanism**  
+  While the memory fraction exceeds `fraction`, the producer goroutine yields control (`runtime.Gosched()`) until sufficient memory becomes available.
+
+- **Logging**  
+  Warns via `obilog.Warnf` when:
+  - Memory pressure persists (every ~1000 yields),
+  - Or wait duration becomes unusually long (>10,000 yielding cycles).
+
+- **Concurrency Model**  
+  - A producer goroutine consumes from the original iterator and pushes items to `newIter`, pausing as needed.
+  - A dedicated consumer goroutine calls `WaitAndClose()` to ensure graceful termination and resource cleanup.
+
+## Semantic Behavior
+
+- **Non-blocking consumer**: Downstream consumers are not stalled; they read from an internal buffered channel (`newIter`).
+- **Adaptive rate control**: The iterator automatically slows down when memory pressure rises, avoiding OOM conditions.
+- **Predictable resource use**: Ensures heap usage stays below the specified `fraction` (e.g., 0.5 → ≤ 50% of total RAM).