Pipeline output json within json

We need to sanitize how we output objects from command execution. Some usage will output stringify json within json.

 

Thread were this started: https://unity.slack.com/archives/C0B006ZK3PF/p1789151821805199
A lot of responses from the Pipeline server are formatted as json strings, giving this kind of abomination: {{

{"success":true,"result":"\{\"status\":\"idle\"}

"}}} (the response for recompile_status). And in default mode, there is still a json string to parse. This tells me we should look into making sure that both modes are "pure". The Pipeline package sometimes responds with objects, sometimes with json strings (get_build_settings returns a real object, recompile_status returns a json string).

Then, this investigation revealed that for short responses like the example above, we are generating 80+% of envlope bytes (my report is in bytes, as a proxy for token efficiency). For recompile_status, we are looking at 75 B in default mode and 372 B in json mode. The agent also claimed this:

dropping the envelope is a 2–5x size win, and default-mode error rendering is the best of every format I tested — two plain lines containing exactly the did-you-mean, nothing else.

My agent also made the recommendation of adding a slim-json mode, dropping the envelope altogether.

Finally, it complained (again) about inconsistent casing in the response format from the Pipeline package:

Casing (Summary.Total vs summary.total)