fix: correct gateway success message to reference gateway-target command

[aidandaly24]

Description

Fix the success message shown after creating a gateway. It previously said "Use 'add tool' to route tools through this gateway" which references the old command name. Updated to say "Use '
add gateway-target' to route targets through this gateway" to match the actual CLI command.

Related Issue

N/A

Documentation PR

N/A

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Other (please describe):

Testing

• I ran npm run test:unit and npm run test:integ
• I ran npm run typecheck
• I ran npm run lint
• If I modified src/assets/, I ran npm run test:update-snapshots and committed the updated snapshots

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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