Replace all Anthropic API calls with Claude Code session (claude -p)

New module claude_session.py provides query() and query_json() that
run prompts via `claude -p` CLI — uses the claude.ai session, zero API cost.

Converted 6 services:
- claims_extractor.py: extract_claims_with_ai
- brainstorm.py: brainstorm_directions
- block_writer.py: write_block (was streaming+thinking, now simple)
- qa_validator.py: claims_coverage check
- style_analyzer.py: 3 API calls (single pass, multi pass, synthesis)
- learning_loop.py: extract_lessons

Only extractor.py still uses Anthropic API (for PDF OCR with Vision).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/services/qa_validator.py

@@ -18,11 +18,9 @@ import logging
 import re
 from uuid import UUID
 
-import anthropic
-
 from legal_mcp import config
 from legal_mcp.config import parse_llm_json
-from legal_mcp.services import db
+from legal_mcp.services import db, claude_session
 
 logger = logging.getLogger(__name__)
 
@@ -89,14 +87,6 @@ def check_neutral_background(blocks: list[dict]) -> dict:
     }
 
 
-_anthropic_client: anthropic.Anthropic | None = None
-
-
-def _get_anthropic() -> anthropic.Anthropic:
-    global _anthropic_client
-    if _anthropic_client is None:
-        _anthropic_client = anthropic.Anthropic(api_key=config.ANTHROPIC_API_KEY)
-    return _anthropic_client
 
 
 CLAIMS_CHECK_PROMPT = """אתה בודק איכות החלטות משפטיות. קיבלת רשימת טענות שהועלו בכתבי הטענות, ואת בלוק הדיון של ההחלטה.
@@ -146,24 +136,15 @@ async def check_claims_coverage(blocks: list[dict], claims: list[dict]) -> dict:
     # Send full discussion — don't truncate
     discussion = yod["content"]
 
-    client = _get_anthropic()
-    message = client.messages.create(
-        model="claude-sonnet-4-20250514",
-        max_tokens=8192,
-        messages=[{
-            "role": "user",
-            "content": f"""{CLAIMS_CHECK_PROMPT}
+    prompt = f"""{CLAIMS_CHECK_PROMPT}
 
 ## טענות ({len(source_claims)}):
 {claims_text}
 
 ## בלוק הדיון:
-{discussion}""",
-        }],
-    )
+{discussion}"""
 
-    raw = message.content[0].text.strip()
-    parsed = parse_llm_json(raw)
+    parsed = claude_session.query_json(prompt, timeout=120)
     if parsed is None:
         logger.warning("Failed to parse claims check: %s", raw[:300])
         # Fallback: assume all covered (don't block export on parse failure)