docs: add agent advice for Testo usage

Author: roxblnfk

docs/ai/agent-advices.md

@@ -0,0 +1,11 @@
+---
+llms: "footer"
+llms_description: "Advice for AI agents working with Testo: run with --json for a parseable result and narrow runs with --filter/--path/--suite while iterating."
+llms_priority: 0
+---
+
+## Advice for Agents
+
+Rules for an AI agent working with Testo.
+
+1. **Run Testo with `--json`, and narrow the run while iterating.** `--json` prints the whole run as one JSON object on stdout and nothing else — no ANSI to parse around. The object holds the summary and a flat `failures[]` list. Parse it instead of the human-readable output. `--json` excludes `--teamcity`. While iterating, target what you change with `--filter`, `--path`, or `--suite`; run the full suite once at the end.