refactor(config): add set_config_value for non-merge replacement

tests/test_config_set_value.py

@@ -0,0 +1,45 @@
+"""Unit test for config.set_config_value (replaces, doesn't merge)."""
+from __future__ import annotations
+
+import yaml
+
+from presa_mano.config import (
+    set_config_value,
+    get_config,
+    load_config,
+    _STATE,
+    _default_config_path,
+)
+
+
+def test_replace_nested_dict_removes_old_keys(tmp_path, monkeypatch):
+    cfg_file = tmp_path / "cfg.yaml"
+    cfg_file.write_text(yaml.safe_dump({
+        "section": {"items": {"a": 1, "b": 2}},
+    }))
+    monkeypatch.setenv("PRESA_MANO_CONFIG", str(cfg_file))
+    # Reset in-memory singleton
+    _STATE["config"] = None
+    _STATE["path"] = None
+    load_config()
+
+    set_config_value(["section", "items"], {"c": 3})
+
+    out = get_config()
+    assert out["section"]["items"] == {"c": 3}
+    # File on disk also updated
+    on_disk = yaml.safe_load(cfg_file.read_text())
+    assert on_disk["section"]["items"] == {"c": 3}
+
+
+def test_create_intermediate_dicts(tmp_path, monkeypatch):
+    cfg_file = tmp_path / "cfg.yaml"
+    cfg_file.write_text(yaml.safe_dump({}))
+    monkeypatch.setenv("PRESA_MANO_CONFIG", str(cfg_file))
+    _STATE["config"] = None
+    _STATE["path"] = None
+    load_config()
+
+    set_config_value(["a", "b", "c"], 42)
+
+    assert get_config() == {"a": {"b": {"c": 42}}}