Add training corpus UI with Nevo proofreading pipeline

- New proofreader service strips Nevo editorial additions (front matter,
  postamble, page headers, watermarks, inline codes) from DOCX/PDF/MD
- PDF pages use Google Vision OCR for clean Hebrew RTL extraction
- New training page at #/training with drag-and-drop upload, automatic
  metadata extraction (decision number, date, categories), reviewable
  preview, and style pattern report grouped by type
- API endpoints: /api/training/{analyze,upload,corpus,patterns,
  analyze-style,analyze-style/status}
- Fix claude_session.query to pipe prompt via stdin, avoiding ARG_MAX
  overflow when analyzing 900K+ char corpus
- CLI scripts for batch proofreading and corpus upload

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

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

@@ -24,6 +24,9 @@ LONG_TIMEOUT = 300  # For complex tasks like block writing
 def query(prompt: str, timeout: int = DEFAULT_TIMEOUT, max_turns: int = 1) -> str:
     """Send a prompt to Claude Code headless and return the text response.
 
+    Passes the prompt via stdin (not argv) to avoid the OS ARG_MAX limit —
+    prompts can be 500K+ chars when analyzing a full style corpus.
+
     Args:
         prompt: The prompt to send.
         timeout: Max seconds to wait.
@@ -36,14 +39,18 @@ def query(prompt: str, timeout: int = DEFAULT_TIMEOUT, max_turns: int = 1) -> st
         RuntimeError: If claude CLI is not available or fails.
     """
     cmd = [
-        "claude", "-p", prompt,
+        "claude", "-p",
         "--output-format", "json",
         "--max-turns", str(max_turns),
     ]
 
     try:
         result = subprocess.run(
-            cmd, capture_output=True, text=True, timeout=timeout,
+            cmd,
+            input=prompt,
+            capture_output=True,
+            text=True,
+            timeout=timeout,
         )
     except FileNotFoundError:
         raise RuntimeError("Claude CLI not found. Install Claude Code or add 'claude' to PATH.")