Upgrade agents to Claude Opus 4.7

- legal-analyst: opus 4.6 → opus 4.7
- legal-proofreader: opus 4.6 → opus 4.7
- legal-writer: sonnet 4.6 → opus 4.7 (complex block writing benefits from stronger model)
- block_writer MODEL_MAP: updated opus ID to 4.7

Opus 4.7 brings: high-res images (2576px), better file-based memory,
improved DOCX generation, and task budgets for agentic loops.

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

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

@@ -27,8 +27,8 @@ logger = logging.getLogger(__name__)
 
 # ── Block configuration ───────────────────────────────────────────
 
-# Output token limits per Anthropic docs (April 2026):
-# Opus 4.6: up to 128K output tokens
+# Output token limits per Anthropic docs:
+# Opus 4.7: up to 128K output tokens (new tokenizer — ~35% more tokens)
 # Sonnet 4.6: up to 64K output tokens
 # Streaming required when max_tokens > 21,333
 BLOCK_CONFIG = {
@@ -48,7 +48,7 @@ BLOCK_CONFIG = {
 
 MODEL_MAP = {
     "sonnet": "claude-sonnet-4-20250514",
-    "opus": "claude-opus-4-20250514",
+    "opus": "claude-opus-4-7",
 }