test(files): add server-detail e2e fixture

Adds server_with_files fixture: seeds alice + a Blueprint + a Server
row pinned to port 27015, then pre-creates
LEFT4ME_ROOT/runtime/<server_id>/merged/ with a single seed file.
The /servers/<id> page lists files from that merged directory (the
kernel-overlayfs view of a running server), which never exists on
dev/test boxes — without the pre-mkdir + seed, the page renders
the empty-state branch instead of file rows.

Server.port is a global UNIQUE constraint on the model, but every
e2e test gets its own SQLite DB, so a fixed L4D2-default port is
fine.

Sets the stage for the Tier 3 hover-download test.

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

l4d2web/tests/e2e/conftest.py

@@ -14,7 +14,7 @@ from werkzeug.serving import make_server
 from l4d2web.app import create_app
 from l4d2web.auth import hash_password
 from l4d2web.db import init_db, session_scope
-from l4d2web.models import Blueprint, Overlay, User
+from l4d2web.models import Blueprint, Overlay, Server, User
 
 
 def _free_port() -> int:
@@ -164,3 +164,65 @@ def files_overlay_server(tmp_path, monkeypatch):
         }
     finally:
         shutdown()
+
+
+@pytest.fixture(scope="function")
+def server_with_files(tmp_path, monkeypatch):
+    """live_server + a Server owned by alice with a populated runtime
+    merged directory. Used by the server-detail e2e tests that exercise
+    file rows + download.
+
+    The /servers/<id> page lists files from
+    LEFT4ME_ROOT/runtime/<server_id>/merged/ (the kernel-overlayfs view
+    of a running server). On a dev/test box no overlayfs is mounted, so
+    the fixture pre-creates that directory and seeds one plain file —
+    enough for the file-tree partial to render rows.
+
+    Yields {base_url, user_id, blueprint_id, server_id, merged_root}.
+    """
+    monkeypatch.setenv("LEFT4ME_ROOT", str(tmp_path))
+    app = _boot_app(tmp_path, monkeypatch)
+
+    with session_scope() as session:
+        user = User(
+            username="alice",
+            password_digest=hash_password("secret"),
+            admin=False,
+        )
+        session.add(user)
+        session.flush()
+        bp = Blueprint(
+            user_id=user.id, name="bp", arguments="[]", config="[]"
+        )
+        session.add(bp)
+        session.flush()
+        # Server.port has a global UNIQUE constraint, but this is a
+        # fresh per-test SQLite DB so any value works — 27015 is the
+        # L4D2 default, semantically obvious.
+        server = Server(
+            user_id=user.id,
+            blueprint_id=bp.id,
+            name="srv",
+            port=27015,
+        )
+        session.add(server)
+        session.flush()
+        user_id = user.id
+        blueprint_id = bp.id
+        server_id = server.id
+
+    merged_root = tmp_path / "runtime" / str(server_id) / "merged"
+    merged_root.mkdir(parents=True)
+    (merged_root / "server.cfg").write_text('hostname "from-merged-runtime"\n')
+
+    base_url, shutdown = _serve(app)
+    try:
+        yield {
+            "base_url": base_url,
+            "user_id": user_id,
+            "blueprint_id": blueprint_id,
+            "server_id": server_id,
+            "merged_root": merged_root,
+        }
+    finally:
+        shutdown()