feat: add background_tasks + list_snapshots tools (v0.3.4)

- background_tasks: SYNO.FileStation.BackgroundTask::list (v3) — paginated
  table of active/recent copy/move/delete/extract/compress tasks
- list_snapshots: SYNO.FileStation.Snapshot::list (v2) — Btrfs snapshots
  per share; maps error 400 to a clear Btrfs-required message
- 20 new tests (107 total)
- SPEC.md and CLAUDE.md updated (26 tools)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/mcp_synology_filestation/tools/filestation.py

@@ -1237,3 +1237,119 @@ def register_filestation(
             return f"Error: {e}"
 
         return f"Deleted favorite for {path}"
+
+    # ── background task + snapshot tools ──────────────────────────────────
+
+    @mcp.tool()
+    async def background_tasks(offset: int = 0, limit: int = 100):
+        """List FileStation background tasks (copy, move, delete, extract, compress, etc.)."""
+        from mcp_synology_filestation.client import SynologyError
+
+        limit = max(1, min(limit, 200))
+        offset = max(0, offset)
+
+        try:
+            data = await client.request(
+                "SYNO.FileStation.BackgroundTask",
+                "list",
+                version=3,
+                params={"offset": offset, "limit": limit},
+            )
+        except SynologyError as e:
+            return f"Error: {e}"
+
+        tasks: list[dict] = data.get("tasks", [])
+        total: int = data.get("total", len(tasks))
+
+        if not tasks:
+            return "No background tasks found."
+
+        rows: list[tuple[str, ...]] = []
+        for task in tasks:
+            taskid = str(task.get("taskid", ""))
+            ttype = str(task.get("type", ""))
+            status = str(task.get("status", ""))
+            path = str(task.get("path", task.get("dest_folder_path", "")))
+            processed = task.get("processed_num_file", 0)
+            total_files = task.get("total_num_file", 0)
+            progress = f"{processed}/{total_files}" if total_files else "-"
+            rows.append((taskid, ttype, status, path, progress))
+
+        headers = ("Task ID", "Type", "Status", "Path", "Progress")
+        col_widths = [max(len(h), *(len(r[i]) for r in rows)) for i, h in enumerate(headers)]
+
+        def _sep() -> str:
+            return "+" + "+".join("-" * (w + 2) for w in col_widths) + "+"
+
+        def _row(vals: tuple[str, ...]) -> str:
+            return "| " + " | ".join(f"{v:<{col_widths[i]}}" for i, v in enumerate(vals)) + " |"
+
+        lines = [_sep(), _row(headers), _sep()]
+        for r in rows:
+            lines.append(_row(r))
+        lines.append(_sep())
+        lines.append(f"\n{total} task(s) total.")
+        if total > offset + limit:
+            lines.append(
+                f"Showing {offset + 1}–{offset + len(tasks)} of {total}. Use offset to page."
+            )
+
+        return "\n".join(lines)
+
+    @mcp.tool()
+    async def list_snapshots(share_path: str, offset: int = 0, limit: int = 100):
+        """List Btrfs snapshots for a shared folder (requires Btrfs volume)."""
+        from mcp_synology_filestation.client import SynologyError
+
+        limit = max(1, min(limit, 500))
+        offset = max(0, offset)
+
+        try:
+            data = await client.request(
+                "SYNO.FileStation.Snapshot",
+                "list",
+                version=2,
+                params={"folder_path": share_path, "offset": offset, "limit": limit},
+            )
+        except SynologyError as e:
+            if e.code == 400:
+                return (
+                    f"Error: Snapshots not available for '{share_path}' — "
+                    "this feature requires a Btrfs-formatted volume."
+                )
+            return f"Error: {e}"
+
+        snapshots: list[dict] = data.get("snapshots", [])
+        total: int = data.get("total", len(snapshots))
+
+        if not snapshots:
+            return f"No snapshots found for '{share_path}'."
+
+        rows: list[tuple[str, ...]] = []
+        for snap in snapshots:
+            snap_id = str(snap.get("id", snap.get("snapshot_id", "")))
+            snap_time = _fmt_time(snap.get("time", snap.get("create_time")))
+            snap_desc = str(snap.get("description", snap.get("desc", "")))
+            snap_lock = "Yes" if snap.get("lock", False) else "No"
+            rows.append((snap_id, snap_time, snap_desc, snap_lock))
+
+        headers = ("Snapshot ID", "Created", "Description", "Locked")
+        col_widths = [max(len(h), *(len(r[i]) for r in rows)) for i, h in enumerate(headers)]
+
+        def _sep() -> str:
+            return "+" + "+".join("-" * (w + 2) for w in col_widths) + "+"
+
+        def _row(vals: tuple[str, ...]) -> str:
+            return "| " + " | ".join(f"{v:<{col_widths[i]}}" for i, v in enumerate(vals)) + " |"
+
+        lines = [_sep(), _row(headers), _sep()]
+        for r in rows:
+            lines.append(_row(r))
+        lines.append(_sep())
+        lines.append(f"\n{total} snapshot(s) for '{share_path}'.")
+        if total > offset + limit:
+            lines.append(
+                f"Showing {offset + 1}–{offset + len(snapshots)} of {total}. Use offset to page."
+            )
+
+        return "\n".join(lines)