feat(storage): X14 Phase 2a — route source-document writes through storage.py

Rewire the source-document staging writes onto the unified storage layer
(INV-STG1), replacing direct shutil.copy2 calls:
- tools/documents.py: case originals + training-corpus uploads
- services/ingest.py: _stage_file (now async) — covers precedent-library,
  internal-decisions, and digests (the canonical intake helper)
- services/digest_library.py: awaits the now-async _stage_file

Each write goes through storage.put_file(..., bucket=DOCUMENTS) with the
DATA_DIR-relative key; the Hebrew original filename rides as object metadata
(INV-STG2), content-type is guessed from the extension. DB path columns are
unchanged (still the absolute dest) — object_key backfill is Phase 3.

Under the default STORAGE_BACKEND=filesystem the bytes land at the exact
legacy on-disk location (put_file → shutil.copy2 to DATA_DIR/key), so this
is zero behaviour change in prod. shutil import dropped where now unused.

tests: +2 staging regression tests (file lands under DATA_DIR at the legacy
path); 20 storage + 22 ingest tests green; 242 collected with no import
breakage.

Derived/export write sites (thumbnails, extracted text, DOCX exports) are
Phase 2b. Keeps G2; advances INV-STG1. Spec: docs/spec/X14-storage-minio.md.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mcp-server/src/legal_mcp/tools/documents.py

@@ -4,12 +4,12 @@ from __future__ import annotations
 
 import hashlib
 import json
-import shutil
+import mimetypes
 from pathlib import Path
 from uuid import UUID
 
 from legal_mcp import config
-from legal_mcp.services import audit, db, git_sync, processor
+from legal_mcp.services import audit, db, git_sync, processor, storage
 from legal_mcp.tools.envelope import empty, err, ok  # GAP-48: SSoT envelope
 
 
@@ -50,11 +50,14 @@ async def document_upload(
             "idempotent_existing": True,
         }, message=f"הקובץ כבר הועלה לתיק {case_number} (זהה ב-hash) — מוחזר הקיים, ללא עיבוד מחדש.")
 
-    # Copy file to case directory
-    case_dir = config.find_case_dir(case_number) / "documents" / "originals"
-    case_dir.mkdir(parents=True, exist_ok=True)
-    dest = case_dir / source.name
-    shutil.copy2(str(source), str(dest))
+    # Stage the original through the unified storage layer (INV-STG1).
+    dest = config.find_case_dir(case_number) / "documents" / "originals" / source.name
+    await storage.put_file(
+        source, dest.relative_to(config.DATA_DIR).as_posix(),
+        bucket=storage.Bucket.DOCUMENTS,
+        content_type=mimetypes.guess_type(source.name)[0],
+        metadata={"filename": source.name},
+    )
 
     # For auto classification, start with "reference" — will be updated after processing
     initial_doc_type = doc_type if doc_type != "auto" else "reference"
@@ -156,10 +159,14 @@ async def document_upload_training(
     }
     subdir = _SUBTYPE_DIRS.get(appeal_subtype, "")
     training_dest = config.TRAINING_DIR / subdir if subdir else config.TRAINING_DIR
-    training_dest.mkdir(parents=True, exist_ok=True)
     dest = training_dest / source.name
     if source.resolve() != dest.resolve():
-        shutil.copy2(str(source), str(dest))
+        await storage.put_file(
+            source, dest.relative_to(config.DATA_DIR).as_posix(),
+            bucket=storage.Bucket.DOCUMENTS,
+            content_type=mimetypes.guess_type(source.name)[0],
+            metadata={"filename": source.name},
+        )
 
     # Extract text and strip Nevo preamble
     text, page_count, _ = await extractor.extract_text(str(dest))