CLI: improve command descriptions in help output (#18486)

* CLI: clarify config vs configure descriptions

* CLI: improve top-level command descriptions

* CLI: make direct command help more descriptive

* CLI: add commands hint to root help

* CLI: show root help hint in implicit help output

* CLI: add help example for command-specific help

* CLI: tweak root subcommand marker spacing

* CLI: mark clawbot as subcommand root in help

* CLI: derive subcommand markers from registry metadata

* CLI: escape help regex CLI name

src/cli/program/register.message.ts

@@ -24,7 +24,7 @@ import { registerMessageThreadCommands } from "./message/register.thread.js";
 export function registerMessageCommands(program: Command, ctx: ProgramContext) {
   const message = program
     .command("message")
-    .description("Send messages and channel actions")
+    .description("Send, read, and manage messages and channel actions")
     .addHelpText(
       "after",
       () =>