Make CLI error paths respect `--json`

[JSONbored]

Problem: Several CLI commands share identical error-handling boilerplate that logs plain text and returns an exit code — but ignores the --json flag on exactly the failure path a monitoring wrapper needs structured output from.

Area: AMS / CLI

Proposal: Make the shared error-handling path check --json and emit a structured error object when set, consistent with each command's success-path output shape.

Deliverables:

• A shared error-formatting helper used by every CLI command, respecting --json.

Acceptance criteria:

• Running any affected command with --json against a failure case returns valid, parseable JSON describing the error.

[linear-code]

JSO-3496