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.fish

@@ -332,8 +332,7 @@ complete -c mcpctl -n "__mcpctl_subcmd_active create group" -l force -d 'Update
 
 # create rbac options
 complete -c mcpctl -n "__mcpctl_subcmd_active create rbac" -l subject -d 'Subject as Kind:name (repeat for multiple)' -x
-complete -c mcpctl -n "__mcpctl_subcmd_active create rbac" -l binding -d 'Role binding as role:resource (e.g. edit:servers, run:projects)' -x
-complete -c mcpctl -n "__mcpctl_subcmd_active create rbac" -l operation -d 'Operation binding (e.g. logs, backup)' -x
+complete -c mcpctl -n "__mcpctl_subcmd_active create rbac" -l roleBindings -d 'Role binding as key:value pairs, e.g. "role:view,resource:servers" or "role:view,resource:servers,name:my-ha" or "action:logs" (repeat for multiple)' -x
 complete -c mcpctl -n "__mcpctl_subcmd_active create rbac" -l force -d 'Update if already exists'
 
 # create prompt options