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

.golangci.yml

@@ -69,6 +69,9 @@ linters:
     goconst:
       min-len: 2
       min-occurrences: 3
+      ignore-string-values:
+        - "csv"
+        - "json"
     gocritic:
       enabled-tags:
         - diagnostic