fix(precedents): Anthropic SDK fallback, format() crash, UI refresh

Three fixes to the precedent library after the first end-to-end test on
403-17 surfaced runtime issues:

1. Anthropic SDK fallback in claude_session. The legal-ai Docker container
   does not ship the `claude` CLI, so every halacha and metadata extraction
   was failing with "Claude CLI not found." Module now tries the CLI first
   (zero-cost local path) and falls back to the Anthropic SDK with
   ANTHROPIC_API_KEY when the binary is absent. Default model is
   claude-sonnet-4-6, overridable via CLAUDE_SDK_MODEL env. The system
   message gets cache_control: ephemeral so multi-chunk runs reuse the
   cached instruction prefix at ~10% read cost. Adds `anthropic` to
   pyproject deps.

2. precedent_metadata_extractor crashed with KeyError because the JSON
   example inside the prompt template contained literal { } characters
   that str.format() interpreted as placeholders. Switched to f-string
   concatenation; the prompt template no longer needs format() at all.

3. Library list query stays stale after upload because the upload
   mutation's onSuccess fires when the POST returns task_id, not when
   SSE reports completion. Added a second invalidate inside the SSE
   watcher in PrecedentUploadSheet so the new row appears with up-to-date
   chunk and halachot counts the moment processing finishes.

Halacha and metadata extractors now route the long static prompt through
the new `system=` parameter so the SDK path actually caches it; the CLI
path concatenates and behaves as before.

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

mcp-server/pyproject.toml

@@ -8,6 +8,7 @@ dependencies = [
     "asyncpg>=0.29.0",
     "pgvector>=0.3.0",
     "voyageai>=0.3.0",
+    "anthropic>=0.45.0",
     "python-dotenv>=1.0.0",
     "pydantic>=2.0.0",
     "pymupdf>=1.25.0",