feat(go-config): multi-format codecs, envc CLI, fixtures, ASRs

- Module github.com/eslider/go-config with env/yaml/json/ini packages
- internal: source, keymap, merge, structconv, bytesutil
- cmd/envc: convert, get, merge
- docs/asr ASR-0001..0008, README/CHANGELOG/AGENTS refresh
- golangci-lint v2 config; tests + fixtures

Co-authored-by: Cursor <cursoragent@cursor.com>

internal/merge/merge_test.go

@@ -0,0 +1,52 @@
+package merge
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestDeepMerge_MapRecursion(t *testing.T) {
+	dst := map[string]any{
+		"a": map[string]any{"x": "1"},
+	}
+	src := map[string]any{
+		"a": map[string]any{"y": "2"},
+	}
+	DeepMerge(dst, src)
+	want := map[string]any{
+		"a": map[string]any{"x": "1", "y": "2"},
+	}
+	if !reflect.DeepEqual(dst, want) {
+		t.Fatalf("got %#v want %#v", dst, want)
+	}
+}
+
+func TestDeepMerge_ScalarLastWins(t *testing.T) {
+	dst := map[string]any{"k": "first"}
+	src := map[string]any{"k": "second"}
+	DeepMerge(dst, src)
+	if dst["k"] != "second" {
+		t.Fatalf("got %v", dst["k"])
+	}
+}
+
+func TestDeepMerge_SliceReplace(t *testing.T) {
+	dst := map[string]any{"s": []any{"a", "b"}}
+	src := map[string]any{"s": []any{"c"}}
+	DeepMerge(dst, src, WithSliceStrategy(Replace))
+	got := dst["s"].([]any)
+	if len(got) != 1 || got[0] != "c" {
+		t.Fatalf("got %#v", got)
+	}
+}
+
+func TestDeepMerge_SliceConcat(t *testing.T) {
+	dst := map[string]any{"s": []any{"a", "b"}}
+	src := map[string]any{"s": []any{"c"}}
+	DeepMerge(dst, src, WithSliceStrategy(Concat))
+	got := dst["s"].([]any)
+	want := []any{"a", "b", "c"}
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("got %#v want %#v", got, want)
+	}
+}