feat: unhide gateway and gateway-target CLI commands

[aidandaly24]

Description

Remove { hidden: true } from the gateway and gateway-target Commander subcommand registrations in GatewayPrimitive.ts and GatewayTargetPrimitive.ts. This makes both commands visible in agentcore add --help and agentcore remove --help output. Updates AGENTS.md to reflect that these primitives are no longer hidden/coming soon.

Related Issue

Closes #

Documentation PR

N/A

Type of Change

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

Testing

How have you tested the change?

• 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

Verified manually:

$ agentcore add --help
Commands:
  agent [options]           Add an agent to the project
  memory [options]          Add a memory to the project
  identity [options]        Add an identity (credential) to the project
  gateway [options]         Add a gateway to the project
  gateway-target [options]  Add a gateway target to the project

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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terms of your choice.

[tejaskash]

LGTM