feat: add views to DEFAULT_SETTINGS and SYNCABLE_KEYS

- Add 'views': [] to DEFAULT_SETTINGS (after 'hidden_sessions')
- Add 'views' to SYNCABLE_KEYS in Session behavior section (after 'hidden_sessions')
- Add 4 new tests: test_views_in_default_settings, test_views_in_syncable_keys,
  test_views_roundtrip_through_save_and_load, test_patch_settings_syncs_views

All 61 tests pass (57 existing + 4 new).

muxplex/settings.py

@@ -22,6 +22,7 @@ DEFAULT_SETTINGS: dict = {
     "default_session": None,
     "sort_order": "manual",
     "hidden_sessions": [],
+    "views": [],
     "window_size_largest": False,
     "auto_open_created": True,
     "new_session_template": "tmux new-session -d -s {name}",
@@ -61,6 +62,7 @@ SYNCABLE_KEYS: frozenset[str] = frozenset(
         # Session behavior
         "sort_order",
         "hidden_sessions",
+        "views",
         "default_session",
         "window_size_largest",
         "auto_open_created",

muxplex/tests/test_settings.py

@@ -972,3 +972,44 @@ def test_apply_synced_settings_does_not_use_time_now():
     apply_synced_settings({"fontSize": 16}, old_ts)
     settings = load_settings()
     assert settings["settings_updated_at"] == old_ts  # exact match, not "close to now"
+
+
+# ============================================================
+# Views key in DEFAULT_SETTINGS and SYNCABLE_KEYS (task-3)
+# ============================================================
+
+
+def test_views_in_default_settings():
+    """DEFAULT_SETTINGS must have 'views' key initialised to []."""
+    assert "views" in DEFAULT_SETTINGS, "DEFAULT_SETTINGS must include 'views'"
+    assert DEFAULT_SETTINGS["views"] == [], (
+        f"views default must be [], got: {DEFAULT_SETTINGS['views']!r}"
+    )
+
+
+def test_views_in_syncable_keys():
+    """SYNCABLE_KEYS must include 'views'."""
+    assert "views" in SYNCABLE_KEYS, "SYNCABLE_KEYS must include 'views'"
+
+
+def test_views_roundtrip_through_save_and_load():
+    """views data with two views containing session arrays survives a save/load cycle."""
+    views_data = [
+        {"name": "Work", "sessions": ["session-a", "session-b"]},
+        {"name": "Personal", "sessions": ["session-c"]},
+    ]
+    save_settings({"views": views_data})
+    result = load_settings()
+    assert result["views"] == views_data, (
+        f"views must survive save/load roundtrip, got: {result['views']!r}"
+    )
+
+
+def test_patch_settings_syncs_views():
+    """patch_settings with 'views' bumps settings_updated_at because views is in SYNCABLE_KEYS."""
+    views_data = [{"name": "Dev", "sessions": ["dev-session"]}]
+    patch_settings({"views": views_data})
+    settings = load_settings()
+    assert settings["settings_updated_at"] > 0, (
+        "settings_updated_at must be > 0 after patching a syncable key (views)"
+    )