feat(cli)!: migrate create rbac bindings to --roleBindings kv syntax

BREAKING: `mcpctl create rbac` no longer accepts `--binding` or
`--operation`. Use `--roleBindings` instead with key:value pairs:

  # resource binding
  --roleBindings role:view,resource:servers
  --roleBindings role:view,resource:servers,name:my-ha

  # operation binding (role:run is implied by action:)
  --roleBindings action:logs

The on-disk YAML shape (`roleBindings: [{role, resource, name?}]` or
`{role:'run', action}`) is unchanged, so Git backups and existing
`apply -f` files continue to work. Only the command-line input format
changes.

The parser is extracted to src/cli/src/commands/rbac-bindings.ts so the
upcoming `mcpctl create mcptoken --bind <kv>` verb can reuse it.

Completions, tests, and the new parser unit test all pass (406/406).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

completions/mcpctl.bash

@@ -194,7 +194,7 @@ _mcpctl() {
             COMPREPLY=($(compgen -W "--description --member --force -h --help" -- "$cur"))
             ;;
           rbac)
-            COMPREPLY=($(compgen -W "--subject --binding --operation --force -h --help" -- "$cur"))
+            COMPREPLY=($(compgen -W "--subject --roleBindings --force -h --help" -- "$cur"))
             ;;
           prompt)
             COMPREPLY=($(compgen -W "-p --project --content --content-file --priority --link -h --help" -- "$cur"))