`svelte-check` exits before writing the full output to pipe when there are a large number of diagnostics

[jackgdll]

Describe the bug

When stdout is a non-TTY pipe (i.e. CI), the output will sometimes be cut off before the end.

Reproduction

1. Run svelte-check against a project that emits ≥1000 ERROR/WARNING diagnostics.
2. Invoke as svelte-check --output machine-verbose with stdout piped (not a TTY).
3. Inspect the captured stdout. Sometimes the output ends mid-stream.

Expected behaviour

The COMPLETED summary line should always be outputted.

System Info

• OS: Linux/Ubuntu (CI)
• IDE: CLI

Which package is the issue about?

svelte-check

Additional Information, eg. Screenshots

No response