Docs/Core: Low-Resource Setups, SkyPilot Option, and No-Recompute (#45)

* docs: add SkyPilot template and instructions for running embeddings/index build on cloud GPU

* docs: add low-resource note in README; point to config guide; suggest OpenAI embeddings, SkyPilot remote build, and --no-recompute

* docs: consolidate low-resource guidance into config guide; README points to it

* cli: add --no-recompute and --no-recompute-embeddings flags; docs: clarify HNSW requires --no-compact when disabling recompute

* docs: dedupe recomputation guidance; keep single Low-resource setups section

* sky: expand leann-build.yaml with configurable params and flags (backend, recompute, compact, embedding options)

* hnsw: auto-disable compact when --no-recompute is used; docs: expand SkyPilot with -e overrides and copy-back example

* docs+sky: simplify SkyPilot flow (auto-build on launch, rsync copy-back); clarify HNSW auto non-compact when no-recompute

* feat: auto compact for hnsw when recompute

* reader: non-destructive portability (relative hints + fallback); fix comments; sky: refine yaml

* cli: unify flags to --recompute/--no-recompute for build/search/ask; docs: update references

* chore: remove

* hnsw: move pruned/no-recompute assertion into backend; api: drop global assertion; docs: will adjust after benchmarking

* cli: use argparse.BooleanOptionalAction for paired flags (--recompute/--compact) across build/search/ask

* docs: a real example on recompute

* benchmarks: fix and extend HNSW+DiskANN recompute vs no-recompute; docs: add fresh numbers and DiskANN notes

* benchmarks: unify HNSW & DiskANN into one clean script; isolate groups, fixed ports, warm-up, param complexity

* docs: diskann recompute

* core: auto-cleanup for LeannSearcher/LeannChat (__enter__/__exit__/__del__); ensure server terminate/kill robustness; benchmarks: use searcher.cleanup(); docs: suggest uv run

* fix: hang on warnings

* docs: boolean flags

* docs: leann help

benchmarks/diskann_vs_hnsw_speed_comparison.py

@@ -10,6 +10,7 @@ This benchmark compares search performance between DiskANN and HNSW backends:
 """
 
 import gc
+import multiprocessing as mp
 import tempfile
 import time
 from pathlib import Path
@@ -17,6 +18,12 @@ from typing import Any
 
 import numpy as np
 
+# Prefer 'fork' start method to avoid POSIX semaphore leaks on macOS
+try:
+    mp.set_start_method("fork", force=True)
+except Exception:
+    pass
+
 
 def create_test_texts(n_docs: int) -> list[str]:
     """Create synthetic test documents for benchmarking."""
@@ -113,10 +120,10 @@ def benchmark_backend(
         ]
         score_validity_rate = len(valid_scores) / len(all_scores) if all_scores else 0
 
-        # Clean up
+        # Clean up (ensure embedding server shutdown and object GC)
         try:
-            if hasattr(searcher, "__del__"):
-                searcher.__del__()
+            if hasattr(searcher, "cleanup"):
+                searcher.cleanup()
             del searcher
             del builder
             gc.collect()
@@ -259,10 +266,21 @@ if __name__ == "__main__":
         print(f"\n❌ Benchmark failed: {e}")
         sys.exit(1)
     finally:
-        # Ensure clean exit
+        # Ensure clean exit (forceful to prevent rare hangs from atexit/threads)
         try:
             gc.collect()
             print("\n🧹 Cleanup completed")
+            # Flush stdio to ensure message is visible before hard-exit
+            try:
+                import sys as _sys
+
+                _sys.stdout.flush()
+                _sys.stderr.flush()
+            except Exception:
+                pass
         except Exception:
             pass
-        sys.exit(0)
+        # Use os._exit to bypass atexit handlers that may hang in rare cases
+        import os as _os
+
+        _os._exit(0)