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/keymap/keymap_test.go

@@ -0,0 +1,25 @@
+package keymap
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestLowerAlnum(t *testing.T) {
+	if got, want := LowerAlnum("sub-Service"), "subservice"; got != want {
+		t.Fatalf("got %q want %q", got, want)
+	}
+}
+
+func TestWalk(t *testing.T) {
+	m := map[string]any{
+		"Sub-Service": map[string]any{"Pool-Size": "10"},
+	}
+	Walk(m, LowerAlnum)
+	want := map[string]any{
+		"subservice": map[string]any{"poolsize": "10"},
+	}
+	if !reflect.DeepEqual(m, want) {
+		t.Fatalf("got %#v want %#v", m, want)
+	}
+}