feat: add output package with Formatter interface (#537)

* docs: add RFC-004 for CLI (cobra) and output design
* feat: add output package with Formatter interface and BrowserData.Each
* fix: golangci config array syntax + add output package tests
* refactor: encapsulated Output as Writer, collect-then-write pattern
* refactor: unified row type with reflection-based CSV/JSON output
* fix: ProfileName empty guard, writeFile close error check, sync RFC-004

output/cookie_editor.go

@@ -0,0 +1,51 @@
+package output
+
+import (
+	"encoding/json"
+	"io"
+
+	"github.com/moond4rk/hackbrowserdata/types"
+)
+
+type cookieEditorFormatter struct{}
+
+func (f *cookieEditorFormatter) ext() string { return "json" }
+
+func (f *cookieEditorFormatter) format(w io.Writer, rows []row) error {
+	entries := make([]cookieEditorEntry, 0, len(rows))
+	for _, r := range rows {
+		c, ok := r.entry.(types.CookieEntry)
+		if !ok {
+			return nil // not cookies, skip
+		}
+		var expDate float64
+		if !c.ExpireAt.IsZero() {
+			expDate = float64(c.ExpireAt.Unix())
+		}
+		entries = append(entries, cookieEditorEntry{
+			Domain:         c.Host,
+			ExpirationDate: expDate,
+			HTTPOnly:       c.IsHTTPOnly,
+			Name:           c.Name,
+			Path:           c.Path,
+			Secure:         c.IsSecure,
+			Value:          c.Value,
+		})
+	}
+
+	enc := json.NewEncoder(w)
+	enc.SetIndent("", "  ")
+	enc.SetEscapeHTML(false)
+	return enc.Encode(entries)
+}
+
+// cookieEditorEntry matches the CookieEditor browser extension's import format.
+type cookieEditorEntry struct {
+	Domain         string  `json:"domain"`
+	ExpirationDate float64 `json:"expirationDate"`
+	HTTPOnly       bool    `json:"httpOnly"`
+	Name           string  `json:"name"`
+	Path           string  `json:"path"`
+	Secure         bool    `json:"secure"`
+	Value          string  `json:"value"`
+}