Support JSON output for --help flags

[sentry-junior]

sentry help --json returns structured help, but the same JSON view does not work with the more common --help forms agents reach for, such as sentry --help --json and sentry issue --help --json.

Current behavior

• sentry help --json works
• sentry --help --json and sentry <command> --help --json do not produce the same JSON help
• Help is split across two UX paths: dedicated sentry help <command...> vs flag-based --help

Gap

• Agents and tooling commonly try --help first
• JSON help is already useful for discovery/tooling, but only on the dedicated help command path

Reported by Jan Peer Stöcklmair.

Requested by Burak Yigit Kaya via Junior.

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View Junior Session in Sentry