test: rewrite functional tests for full CLI coverage

Consolidate all tests into functional_test.go — remove duplicate
new_commands_test.go. Replace SDK-only tests with actual CLI binary
invocations. Add missing coverage for: issue list, issue view,
issue comment, issue create, issue edit title, repo view, repo list,
release view, --json flag on issue list/view and pr list.
All tests now use -R flag consistently.

35 pass, 0 fail, 3 expected skips (pr view/diff need PRs, clone needs auth).

tests/functional/fixtures.go

@@ -9,6 +9,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"code.gitea.io/sdk/gitea"
@@ -295,3 +296,39 @@ func (env *TestEnv) RunCLI(args ...string) *CLIResult {
 
 	return result
 }
+
+// runCLIWithStdin executes the CLI binary with the given args and pipes input to stdin.
+func (env *TestEnv) runCLIWithStdin(input string, args ...string) *CLIResult {
+	cmd := exec.Command(env.GetBinaryPath(), args...)
+	cmd.Env = os.Environ()
+	cmd.Stdin = strings.NewReader(input)
+
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	exitCode := 0
+	if err != nil {
+		if exitErr, ok := err.(*exec.ExitError); ok {
+			exitCode = exitErr.ExitCode()
+		}
+	}
+
+	result := &CLIResult{
+		Stdout:   stdout.String(),
+		Stderr:   stderr.String(),
+		ExitCode: exitCode,
+	}
+
+	env.T.Logf("Command: %s %v", env.GetBinaryPath(), args)
+	env.T.Logf("Exit code: %d", exitCode)
+	if stdout.Len() > 0 {
+		env.T.Logf("Stdout:\n%s", result.Stdout)
+	}
+	if stderr.Len() > 0 {
+		env.T.Logf("Stderr:\n%s", result.Stderr)
+	}
+
+	return result
+}