feat(cli): TTY-aware return + OSC52 clipboard with terminal gating

cli/cmd_vault.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/base64"
 	"fmt"
 	"os"
 	"os/exec"
@@ -144,6 +145,43 @@ func bwGet(run cmdRunner, env []string, field, name string) (string, error) {
 	return run("bw", bwGetArgs(field, name), env)
 }
 
+func returnMode(isTTY bool) string {
+	if isTTY {
+		return "clipboard"
+	}
+	return "stdout"
+}
+
+// stdoutIsTTY reports whether stdout is a character device (a terminal).
+func stdoutIsTTY() bool {
+	fi, err := os.Stdout.Stat()
+	if err != nil {
+		return false
+	}
+	return fi.Mode()&os.ModeCharDevice != 0
+}
+
+// osc52 returns the OSC 52 escape that makes the local terminal copy payload to
+// the system clipboard (works over SSH; no X11). osc52clear copies empty.
+func osc52(payload string) string {
+	return "\x1b]52;c;" + base64.StdEncoding.EncodeToString([]byte(payload)) + "\a"
+}
+func osc52clear() string { return "\x1b]52;c;\a" }
+
+// terminalAllowed gates OSC 52: only terminals known to honor clipboard writes,
+// else we'd dump the secret's base64 into scrollback on unsupported terminals.
+func terminalAllowed(term, termProgram string) bool {
+	t := strings.ToLower(term)
+	p := strings.ToLower(termProgram)
+	for _, ok := range []string{"kitty", "alacritty", "foot", "wezterm", "ghostty", "tmux", "screen"} {
+		if strings.Contains(t, ok) || strings.Contains(p, ok) {
+			return true
+		}
+	}
+	// xterm proper supports it only when the program is a known-good emulator.
+	return false
+}
+
 func vaultSetup(args []string) error  { return fmt.Errorf("not implemented") }
 func vaultStatus(args []string) error { return fmt.Errorf("not implemented") }
 func vaultList(args []string) error   { return fmt.Errorf("not implemented") }

cli/cmd_vault_test.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/base64"
 	"reflect"
 	"strings"
 	"testing"
@@ -140,3 +141,38 @@ func TestBwUnlockReturnsSession(t *testing.T) {
 		t.Fatalf("unlock argv = %v", last)
 	}
 }
+
+func TestReturnMode(t *testing.T) {
+	if returnMode(true) != "clipboard" || returnMode(false) != "stdout" {
+		t.Fatal("returnMode wrong")
+	}
+}
+
+func TestOSC52Encode(t *testing.T) {
+	got := osc52("secret")
+	want := "\x1b]52;c;" + base64.StdEncoding.EncodeToString([]byte("secret")) + "\a"
+	if got != want {
+		t.Fatalf("osc52 = %q want %q", got, want)
+	}
+	if osc52clear() != "\x1b]52;c;\a" {
+		t.Fatalf("osc52clear wrong: %q", osc52clear())
+	}
+}
+
+func TestTerminalAllowed(t *testing.T) {
+	allow := []struct{ term, prog string }{
+		{"xterm-kitty", ""}, {"alacritty", ""}, {"foot", ""}, {"tmux-256color", ""},
+		{"screen-256color", ""}, {"xterm-256color", "WezTerm"}, {"xterm-256color", "ghostty"},
+	}
+	for _, c := range allow {
+		if !terminalAllowed(c.term, c.prog) {
+			t.Errorf("terminalAllowed(%q,%q) = false, want true", c.term, c.prog)
+		}
+	}
+	deny := []struct{ term, prog string }{{"dumb", ""}, {"", ""}, {"vt100", ""}}
+	for _, c := range deny {
+		if terminalAllowed(c.term, c.prog) {
+			t.Errorf("terminalAllowed(%q,%q) = true, want false", c.term, c.prog)
+		}
+	}
+}