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/_search_llm.py

@@ -0,0 +1,67 @@
+"""Claude client abstraction. SDK preferred, `claude -p` CLI fallback."""
+
+from __future__ import annotations
+
+import os
+import shutil
+import subprocess
+from typing import Callable
+
+LLMCaller = Callable[..., str]  # (prompt, *, model, max_tokens) -> response text
+
+
+def _have_anthropic_sdk() -> bool:
+    try:
+        import anthropic  # noqa: F401
+        return True
+    except ImportError:
+        return False
+
+
+def _have_claude_cli() -> bool:
+    return shutil.which("claude") is not None
+
+
+def _call_via_sdk(prompt: str, model: str, max_tokens: int) -> str:
+    import anthropic
+    client = anthropic.Anthropic()
+    response = client.messages.create(
+        model=model,
+        max_tokens=max_tokens,
+        messages=[{"role": "user", "content": prompt}],
+    )
+    return response.content[0].text
+
+
+def _call_via_cli(prompt: str, model: str, max_tokens: int) -> str:
+    """Shell out to Claude Code CLI. max_tokens is ignored (CLI handles defaults)."""
+    result = subprocess.run(
+        ["claude", "-p", prompt, "--model", model],
+        capture_output=True,
+        text=True,
+        check=True,
+        timeout=60,
+    )
+    return result.stdout.strip()
+
+
+def call_claude(
+    prompt: str,
+    *,
+    model: str = "claude-haiku-4-5",
+    max_tokens: int = 1000,
+) -> str:
+    """Send a prompt to Claude.
+
+    Tries the anthropic SDK first (requires ANTHROPIC_API_KEY), falls back to
+    the `claude -p` CLI if available. Raises RuntimeError if neither works.
+    """
+    if _have_anthropic_sdk() and os.getenv("ANTHROPIC_API_KEY"):
+        return _call_via_sdk(prompt, model, max_tokens)
+    if _have_claude_cli():
+        return _call_via_cli(prompt, model, max_tokens)
+    raise RuntimeError(
+        "No Claude client available. Either:\n"
+        "  - Install the `anthropic` SDK and set ANTHROPIC_API_KEY, or\n"
+        "  - Install Claude Code CLI (`claude` on PATH)"
+    )