feat(notion-search): add query expansion via Claude Haiku

Generates up to 5 query variants (synonyms + cross-language KR↔EN) so
later Notion API search can union over them. Permissive failure modes:
LLM error or non-JSON response falls back to [original] with stderr
warning. Dedupes and caps variants.

4 tests: variants list, dedup+cap, JSON-parse fallback, exception
fallback. 12 passing total.

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

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

@@ -0,0 +1,78 @@
+#!/usr/bin/env python3
+"""Notion semantic search — query expansion + LLM rerank over Notion API search.
+
+CLI: python3 notion_search.py "query" [--databases ID,...] [--filter JSON] \
+                                       [--limit N] [--no-rerank] [--no-expand] \
+                                       [--no-cache] [--json]
+"""
+
+from __future__ import annotations
+
+import json
+import re
+import sys
+from typing import Callable, List
+
+from _search_llm import call_claude as default_llm_caller
+
+EXPAND_PROMPT = """You are a query expander for a Notion semantic search tool. Generate up to {n} variants of the user's query that capture related concepts, synonyms, and cross-language alternates (especially Korean ↔ English).
+
+Rules:
+- Always include the original query verbatim as the first variant.
+- Variants should help find pages that the original query might miss due to keyword-only search.
+- For Korean queries, include English synonyms; for English queries, include Korean alternates if the topic has common Korean usage.
+- Keep variants concise (under 8 words each).
+
+Query: {query}
+
+Return ONLY a JSON array of strings, no prose. Example:
+["original query", "synonym variant", "cross-language variant"]"""
+
+
+def expand_query(
+    query: str,
+    *,
+    llm_caller: Callable[..., str] = None,
+    max_variants: int = 5,
+) -> List[str]:
+    """Expand a query into related variants. Returns [query] on any failure."""
+    if llm_caller is None:
+        llm_caller = default_llm_caller
+
+    prompt = EXPAND_PROMPT.format(n=max_variants, query=query)
+
+    try:
+        response = llm_caller(prompt)
+    except Exception as exc:
+        print(f"Warning: query expansion failed ({exc}); using original query only",
+              file=sys.stderr)
+        return [query]
+
+    # Be permissive: extract the first JSON array from the response.
+    match = re.search(r'\[.*\]', response, re.DOTALL)
+    if not match:
+        print(f"Warning: query expansion returned no JSON array; using original query only",
+              file=sys.stderr)
+        return [query]
+
+    try:
+        variants = json.loads(match.group(0))
+    except json.JSONDecodeError:
+        print(f"Warning: query expansion returned invalid JSON; using original query only",
+              file=sys.stderr)
+        return [query]
+
+    if not isinstance(variants, list) or not all(isinstance(v, str) for v in variants):
+        return [query]
+
+    # Always include the original query first; dedupe; cap at max_variants.
+    seen = set()
+    result = []
+    for v in [query] + variants:
+        v = v.strip()
+        if v and v not in seen:
+            seen.add(v)
+            result.append(v)
+        if len(result) >= max_variants:
+            break
+    return result