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>

cmd/envc/main.go

@@ -0,0 +1,28 @@
+package main
+
+import (
+	"fmt"
+	"os"
+)
+
+func main() {
+	stdin, stdout, stderr := os.Stdin, os.Stdout, os.Stderr
+	args := os.Args[1:]
+	if len(args) < 1 {
+		_, _ = fmt.Fprintln(stderr, "usage: envc <convert|get|merge> [flags]")
+		os.Exit(2)
+	}
+	var code int
+	switch args[0] {
+	case "convert":
+		code = RunConvert(args[1:], stdin, stdout, stderr)
+	case "get":
+		code = RunGet(args[1:], stdin, stdout, stderr)
+	case "merge":
+		code = RunMerge(args[1:], stdin, stdout, stderr)
+	default:
+		_, _ = fmt.Fprintf(stderr, "unknown command %q\n", args[0])
+		code = 2
+	}
+	os.Exit(code)
+}