feat: add haystack — expert skill for production search pipelines

Greenfield SkillOpt: 3 epochs for deepset Haystack skill.
Pipeline DAG model, document stores, retrievers, evaluation, deployment.

Epoch 1 — Prominence: Hard-gate on Pipeline DAG vs LCEL pipe model
Epoch 2 — Decision Guidance: Where to Start, Framework Routing Guide
Epoch 3 — Pattern Expansion: Hybrid RAG pattern, evaluation pipeline, deployment

11 files: SKILL.md, 6 references, 3 templates, 1 script.

haystack/scripts/check-setup.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+"""Verify Haystack installation."""
+
+import sys
+
+REQUIRED = ["haystack", "haystack_components"]
+OPTIONAL = ["hayhooks"]
+
+for pkg in REQUIRED:
+    try:
+        __import__(pkg.replace("-", "_"))
+        print(f"  [OK] {pkg}")
+    except ImportError:
+        print(f"  [FAIL] {pkg} — install with pip install {pkg}")
+        sys.exit(1)
+
+for pkg in OPTIONAL:
+    try:
+        __import__(pkg.replace("-", "_"))
+        print(f"  [OK] {pkg} (optional)")
+    except ImportError:
+        print(f"  [—] {pkg} (optional, not installed)")
+
+# Test basic pipeline creation
+from haystack import Pipeline
+p = Pipeline()
+print("  [OK] Pipeline creation works")
+
+print("\nHaystack setup check: ALL REQUIRED PACKAGES OK")