fix: validate gateway group membership before mutations

[davefmurray]

Gateway group commands currently skip the membership validation already enforced by the file backend. For example, gbot --gateway groups add Launch Launch sends a nested-group mutation, and removing the last member sends an empty membership list. Repeated references to the same bot are also sent as duplicate IDs, while the CLI advertises a six-member limit that gateway mode does not enforce.

This change resolves and deduplicates members before enforcing the existing one-to-six-bot rule, rejects nested groups, and rejects bot targets for group membership changes. Validation runs before createGroup or setGroupMembers mutations; add/remove inherit it through the existing set path. Includes a patch changeset.

Validation:

• 17 gateway tests cover create/set/add/remove, alias deduplication at the six-member boundary, invalid memberships, invalid targets, and successful mutations. 14 fail against the original implementation.
• npm test: 41 passed.
• Node 18 compatibility suite: 41 passed.
• npx --yes publint@0.3.24: passed.
• Packed, installed into a temporary prefix, and ran gbot --help: passed.
• git diff --check: passed.

Gateway responses are mocked; no live account mutations were performed.

[changeset-bot]

🦋 Changeset detected

Latest commit: 2e6d835

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
grok-bot-cli	Patch

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