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.go

@@ -0,0 +1,56 @@
+// Package keymap normalizes map keys recursively for cross-format matching.
+package keymap
+
+import "strings"
+
+// Normalizer transforms a single path segment or key string.
+type Normalizer func(string) string
+
+// LowerAlnum lowercases and strips any rune that is not [a-z0-9].
+func LowerAlnum(s string) string {
+	var b strings.Builder
+	b.Grow(len(s))
+	for _, r := range strings.ToLower(s) {
+		if r >= 'a' && r <= 'z' || r >= '0' && r <= '9' {
+			b.WriteRune(r)
+		}
+	}
+	return b.String()
+}
+
+// Identity returns s unchanged.
+func Identity(s string) string { return s }
+
+// Walk recursively rewrites every map key in place using n. Slices of maps are walked.
+func Walk(m map[string]any, n Normalizer) {
+	if m == nil || n == nil {
+		return
+	}
+	keys := make([]string, 0, len(m))
+	for k := range m {
+		keys = append(keys, k)
+	}
+	for _, k := range keys {
+		v := m[k]
+		delete(m, k)
+		nk := n(k)
+		if nk == "" {
+			nk = k
+		}
+		switch vv := v.(type) {
+		case map[string]any:
+			Walk(vv, n)
+			m[nk] = vv
+		case []any:
+			for i := range vv {
+				if sm, ok := vv[i].(map[string]any); ok {
+					Walk(sm, n)
+					vv[i] = sm
+				}
+			}
+			m[nk] = vv
+		default:
+			m[nk] = v
+		}
+	}
+}

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)
+	}
+}