feat(notion-search): add LLM client abstraction with SDK + CLI fallback

First task of Phase 3b-i (notion semantic search). Adds _search_llm.py
that dispatches to the anthropic SDK when ANTHROPIC_API_KEY is set,
falls back to `claude -p` CLI otherwise, and raises a clear setup
error if neither works. Symlinks _notion_compat.py from 32-notion-writer
so both skills share one source of truth.

3 tests cover the three dispatch paths.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

custom-skills/31-notion-organizer/code/scripts/test_notion_search.py

@@ -0,0 +1,76 @@
+#!/usr/bin/env python3
+"""Tests for notion_search.py — run with `python3 test_notion_search.py`."""
+
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent))
+
+
+def _assert(cond, msg):
+    if not cond:
+        print(f"  ✗ FAIL: {msg}")
+        raise SystemExit(1)
+    print(f"  ✓ {msg}")
+
+
+def test_call_claude_dispatches_to_sdk_when_available():
+    """When SDK is available and ANTHROPIC_API_KEY is set, use SDK path."""
+    import os
+    from unittest.mock import patch
+    import _search_llm
+
+    with patch.object(_search_llm, "_have_anthropic_sdk", return_value=True), \
+         patch.dict(os.environ, {"ANTHROPIC_API_KEY": "sk-fake"}), \
+         patch.object(_search_llm, "_call_via_sdk", return_value="sdk-response") as sdk_mock, \
+         patch.object(_search_llm, "_call_via_cli", return_value="cli-response") as cli_mock:
+        result = _search_llm.call_claude("hello")
+        _assert(result == "sdk-response", "SDK path returned its response")
+        _assert(sdk_mock.called, "SDK path was invoked")
+        _assert(not cli_mock.called, "CLI path was NOT invoked")
+
+
+def test_call_claude_falls_back_to_cli_when_no_sdk():
+    """When SDK is missing but CLI is available, use CLI path."""
+    from unittest.mock import patch
+    import _search_llm
+
+    with patch.object(_search_llm, "_have_anthropic_sdk", return_value=False), \
+         patch.object(_search_llm, "_have_claude_cli", return_value=True), \
+         patch.object(_search_llm, "_call_via_cli", return_value="cli-response") as cli_mock:
+        result = _search_llm.call_claude("hello")
+        _assert(result == "cli-response", "CLI path returned its response")
+        _assert(cli_mock.called, "CLI path was invoked")
+
+
+def test_call_claude_raises_when_neither_available():
+    """Both clients missing → RuntimeError with setup hint."""
+    from unittest.mock import patch
+    import _search_llm
+
+    with patch.object(_search_llm, "_have_anthropic_sdk", return_value=False), \
+         patch.object(_search_llm, "_have_claude_cli", return_value=False):
+        try:
+            _search_llm.call_claude("hello")
+            _assert(False, "should have raised RuntimeError")
+        except RuntimeError as exc:
+            _assert("ANTHROPIC_API_KEY" in str(exc) or "claude" in str(exc).lower(),
+                    "error mentions setup options")
+
+
+def run_all():
+    tests = [
+        test_call_claude_dispatches_to_sdk_when_available,
+        test_call_claude_falls_back_to_cli_when_no_sdk,
+        test_call_claude_raises_when_neither_available,
+    ]
+    for t in tests:
+        print(f"\n{t.__name__}")
+        t()
+    print("\n" + "=" * 50)
+    print(f"✅ All {len(tests)} tests passed")
+    print("=" * 50)
+
+
+if __name__ == "__main__":
+    run_all()