fix(cli): exit 0 when invoking parent commands without a subcommand (#73077)

Several `openclaw <parent>` commands (channels, plugins, approvals, devices,
cron, mcp) were exiting with code 1 when invoked bare, while printing the
same help-style content that `<parent> --help` produces (which exits 0).
This broke `&&` chains and surfaced a misleading
`ELIFECYCLE Command failed with exit code 1.` line under pnpm.

Add a small `applyParentDefaultHelpAction(cmd)` helper in
`src/cli/program/parent-default-help.ts` that attaches a default action
which prints the parent's own help and sets `process.exitCode = 0`. The
helper is a no-op when the parent already has its own action (e.g.
`agents` defaulting to `agents list`), so existing intentional defaults
are preserved.

Apply it to the six core parents listed in #73077.

src/cli/program/parent-default-help.ts

@@ -0,0 +1,22 @@
+import type { Command } from "commander";
+
+/**
+ * Wire a parent command so that invoking it without a subcommand prints the
+ * parent's own help and exits with status `0`.
+ *
+ * Commander's default behavior for a parent with subcommands is to print help
+ * and set `process.exitCode = 1`, which differs from `<parent> --help` (which
+ * exits 0). That asymmetry breaks shell `&&` chains and surfaces a misleading
+ * `ELIFECYCLE Command failed with exit code 1.` line for users running through
+ * pnpm. See #73077.
+ *
+ * Apply this helper only to parent commands that do not have their own default
+ * action. Commander does not expose a public "has action handler" API, so
+ * callers keep that ownership explicit instead of probing private internals.
+ */
+export function applyParentDefaultHelpAction(parent: Command): void {
+  parent.action(() => {
+    parent.outputHelp();
+    process.exitCode = 0;
+  });
+}