feat(browser_list): añade campo headless por master

browser_list ahora reporta si cada Chromium master se lanzo en modo headless,
detectado por el flag de arranque (--headless / --headless=new / --headless=old)
leido del cmdline. Una sola llamada devuelve navegadores activos + CDP + headless,
sin tener que conectar a cada pagina para fingerprintear.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tools_lifecycle.go

@@ -55,6 +55,7 @@ type chromiumMaster struct {
 	UserDataDir string `json:"user_data_dir"` // value of --user-data-dir
 	CDPPort     string `json:"cdp_port"`      // value of --remote-debugging-port ("" if none)
 	HasCDP      bool   `json:"has_cdp"`
+	Headless    bool   `json:"headless"` // true if launched with --headless / --headless=new / --headless=old
 }
 
 // parseCmdline turns the raw bytes of /proc/<pid>/cmdline into argv.
@@ -154,9 +155,23 @@ func parseChromiumMaster(pid int, args []string) (chromiumMaster, bool) {
 		UserDataDir: udd,
 		CDPPort:     port,
 		HasCDP:      hasCDP,
+		Headless:    isHeadless(args),
 	}, true
 }
 
+// isHeadless reports whether the process was launched in headless mode. Chromium
+// spells it "--headless", "--headless=new" or "--headless=old"; matching the
+// "--headless" prefix covers all three. There is no current Chromium flag that
+// starts with "--headless" but means something else, so the prefix is safe.
+func isHeadless(args []string) bool {
+	for _, a := range args {
+		if a == "--headless" || strings.HasPrefix(a, "--headless=") {
+			return true
+		}
+	}
+	return false
+}
+
 // firstNonEmpty returns the flag value or "" if absent.
 func firstNonEmpty(args []string, name string) string {
 	v, _ := flagValue(args, name)
@@ -256,7 +271,7 @@ type browserListArgs struct{}
 
 func browserListTool() mcp.Tool {
 	return mcp.NewTool("browser_list",
-		mcp.WithDescription("List the running Chromium MASTER processes (one per user-data-dir master, NOT zygote/gpu/renderer children). For each: pid, profile (--profile-directory value), user_data_dir, cdp_port (--remote-debugging-port value, empty if none), has_cdp. Returns a JSON array. Read-only."),
+		mcp.WithDescription("List the running Chromium MASTER processes (one per user-data-dir master, NOT zygote/gpu/renderer children). For each: pid, profile (--profile-directory value), user_data_dir, cdp_port (--remote-debugging-port value, empty if none), has_cdp, headless (true if launched with --headless). Returns a JSON array. Read-only."),
 	)
 }
 

tools_lifecycle_test.go

@@ -195,3 +195,31 @@ func TestParseCmdline(t *testing.T) {
 		t.Errorf("cmdline vacio debe devolver nil")
 	}
 }
+
+// TestIsHeadless valida la deteccion de modo headless por el flag de lanzamiento:
+// --headless, --headless=new y --headless=old cuentan; su ausencia es headed.
+func TestIsHeadless(t *testing.T) {
+	cases := []struct {
+		name string
+		args []string
+		want bool
+	}{
+		{"sin flag (headed)", []string{"/usr/lib/chromium/chromium", "--user-data-dir=/tmp/x"}, false},
+		{"--headless legacy", []string{"/usr/lib/chromium/chromium", "--headless", "--user-data-dir=/tmp/x"}, true},
+		{"--headless=new", []string{"/usr/lib/chromium/chromium", "--headless=new"}, true},
+		{"--headless=old", []string{"/usr/lib/chromium/chromium", "--headless=old"}, true},
+	}
+	for _, c := range cases {
+		t.Run(c.name, func(t *testing.T) {
+			if got := isHeadless(c.args); got != c.want {
+				t.Errorf("isHeadless(%v) = %v, want %v", c.args, got, c.want)
+			}
+		})
+	}
+
+	// El master headed real (cmdline colapsado por espacios) debe reportar headless=false.
+	headed := parseCmdline([]byte("/usr/lib/chromium/chromium --remote-debugging-port=9333 --user-data-dir=/tmp/browser_mcp_userdata"))
+	if m, ok := parseChromiumMaster(1, headed); !ok || m.Headless {
+		t.Errorf("master headed: ok=%v headless=%v, want ok=true headless=false", ok, m.Headless)
+	}
+}