Add --format=jsonl for newline-delimited JSON output

[holmboe]

Context

With the fix in #178, --format=json now outputs a valid JSON array when showing multiple tasks. This is correct for JSON but means the entire output must be buffered before writing.

Proposal

Add --format=jsonl (or --format=ndjson) that outputs one JSON object per line, with no wrapping array. This is useful for:

• Streaming output (process tasks as they arrive)
• Piping to tools like jq -c that expect one object per line
• Appending to log files

Example

$ phabfive --format=jsonl maniphest show T123 T456
{"Link":"https://phorge.example.com/T123","Task":{...}}
{"Link":"https://phorge.example.com/T456","Task":{...}}

References

• JSON Lines
• ndjson