fix(browser_list): parse cmdline colapsado por espacios de Chromium

/proc/<pid>/cmdline normalmente separa argv por NUL, pero Chromium reescribe
su titulo de proceso in-place colapsando la region de argv a una sola cadena
separada por espacios. readProcCmdline asumia solo NUL, asi que para los
masters de Chromium devolvia un unico argv[0] gigante: isChromiumExe y el
prefijo --user-data-dir= fallaban y browser_list devolvia [] aunque hubiera
navegadores vivos.

Extrae parseCmdline (pura, testeable) con fallback a split por espacios cuando
no hay NUL. Test cubre ambos formatos + regresion de deteccion de master.

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

tools_lifecycle.go

@@ -57,14 +57,31 @@ type chromiumMaster struct {
 	HasCDP      bool   `json:"has_cdp"`
 }
 
-// readProcCmdline reads /proc/<pid>/cmdline and splits it on NUL into argv.
-// Returns nil if the process is gone or unreadable.
-func readProcCmdline(pid int) []string {
-	b, err := os.ReadFile(filepath.Join("/proc", strconv.Itoa(pid), "cmdline"))
-	if err != nil || len(b) == 0 {
+// parseCmdline turns the raw bytes of /proc/<pid>/cmdline into argv.
+//
+// Canonically the kernel separates arguments with NUL bytes. But Chromium (and
+// other programs that rewrite their process title in place) collapse the argv
+// region into a single space-separated string, losing the NUL separators. In
+// that case splitting on NUL yields a single giant element holding the whole
+// command line, which breaks argv[0] detection and "--flag=" prefix matching.
+//
+// So: if the data still carries NUL separators we split on NUL (the correct,
+// space-safe path). Otherwise we fall back to splitting on whitespace. The
+// fallback is best-effort and would mis-split a flag value containing spaces
+// (e.g. a user-data-dir path with a space), but Chromium's own flags don't, so
+// it recovers the master-detection flags (--user-data-dir, --type=,
+// --remote-debugging-port, --profile-directory) reliably in practice.
+func parseCmdline(b []byte) []string {
+	s := strings.TrimRight(string(b), "\x00")
+	if s == "" {
 		return nil
 	}
-	raw := strings.Split(string(b), "\x00")
+	var raw []string
+	if strings.Contains(s, "\x00") {
+		raw = strings.Split(s, "\x00")
+	} else {
+		raw = strings.Fields(s)
+	}
 	args := make([]string, 0, len(raw))
 	for _, a := range raw {
 		if a != "" {
@@ -74,6 +91,16 @@ func readProcCmdline(pid int) []string {
 	return args
 }
 
+// readProcCmdline reads /proc/<pid>/cmdline and parses it into argv.
+// Returns nil if the process is gone or unreadable.
+func readProcCmdline(pid int) []string {
+	b, err := os.ReadFile(filepath.Join("/proc", strconv.Itoa(pid), "cmdline"))
+	if err != nil || len(b) == 0 {
+		return nil
+	}
+	return parseCmdline(b)
+}
+
 // flagValue returns the value of a "--name=value" flag from argv, plus whether it
 // was present. Matches the exact "--name=" prefix; the first occurrence wins.
 func flagValue(args []string, name string) (string, bool) {