feat(mosaic): alphabetize and group mosaic --help output

Enables sortSubcommands on the root program, sessions group, gateway
group, and mission group so all subcommand listings render A-Z. Appends
a Command Groups section via addHelpText to group commands by role
(Runtime, Gateway, Framework, Platform, Runtimes).

Implements CU-04-01, CU-04-02, CU-04-03 from mission cli-unification-20260404.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/mosaic/src/cli.ts

@@ -33,7 +33,23 @@ try {
 
 const program = new Command();
 
-program.name('mosaic').description('Mosaic Stack CLI').version(CLI_VERSION);
+program
+  .name('mosaic')
+  .description('Mosaic Stack CLI')
+  .version(CLI_VERSION)
+  .configureHelp({ sortSubcommands: true })
+  .addHelpText(
+    'after',
+    `
+Command Groups:
+
+  Runtime:    tui, login, sessions
+  Gateway:    gateway
+  Framework:  agent, bootstrap, coord, doctor, init, launch, mission, prdy, seq, sync, upgrade, wizard, yolo
+  Platform:   update
+  Runtimes:   claude, codex, opencode, pi
+`,
+  );
 
 // ─── runtime launchers + framework commands ────────────────────────────
 
@@ -214,7 +230,10 @@ program
 
 // ─── sessions ───────────────────────────────────────────────────────────
 
-const sessionsCmd = program.command('sessions').description('Manage active agent sessions');
+const sessionsCmd = program
+  .command('sessions')
+  .description('Manage active agent sessions')
+  .configureHelp({ sortSubcommands: true });
 
 sessionsCmd
   .command('list')

packages/mosaic/src/commands/gateway.ts

@@ -30,6 +30,7 @@ export function registerGatewayCommand(program: Command): void {
     .option('-h, --host <host>', 'Gateway host', 'localhost')
     .option('-p, --port <port>', 'Gateway port', '14242')
     .option('-t, --token <token>', 'Admin API token')
+    .configureHelp({ sortSubcommands: true })
     .action(() => {
       gw.outputHelp();
     });

packages/mosaic/src/commands/mission.ts

@@ -47,6 +47,7 @@ export function registerMissionCommand(program: Command) {
     .option('--update <idOrName>', 'Update a mission')
     .option('--project <idOrName>', 'Scope to project')
     .argument('[id]', 'Show mission detail by ID')
+    .configureHelp({ sortSubcommands: true })
     .action(
       async (
         id: string | undefined,