Function emit_json_line 

pub fn emit_json_line<T: Serialize>(value: &T)

Writes compact JSON to stdout, silently ignoring serialization and I/O errors. Designed for NDJSON streaming where partial output is acceptable.

GAP-SG-142: NDJSON deliberately bypasses crate::agent_surface. The stream contract is one record per line and the shaping surface is defined over a complete envelope; filtering or capping a stream line by line would change what “one record” means for every consumer already parsing it.

The exclusion is a decision, not an oversight — do not “fix” it wholesale. The flags split into two groups:

• Set-wide, never applicable here: --max-items, --sort and --dedupe-by need the complete result set before they can decide what to emit. A stream has no complete set by construction.
• Per-line, safe to add later: --select and --truncate-content are stateless per record, and --max-output-bytes would be genuinely valuable as a running budget across the stream. Wiring those three here is a deliberate future extension; it needs its own contract decision about what a consumer sees when the running budget is exhausted mid-stream (truncated line? terminator record? silent stop?).