feat(councils): add preflight, schema-driven outputs, and artifact reporting

docs/api/COUNCILS.md

@@ -38,6 +38,16 @@ Flynn supports a deterministic dual-council orchestration pipeline (`council.run
 }
 ```
 
+`council.run` output behavior:
+
+- Tool output returns a concise execution brief suitable for TUI/chat surfaces.
+- Full artifacts are persisted to disk:
+  - `${FLYNN_DATA_DIR}/councils/` when `FLYNN_DATA_DIR` is set
+  - otherwise `~/.local/share/flynn/councils/`
+- Per run, Flynn writes:
+  - `<timestamp>-<slug>.md` summary report with conversation trace and embedded raw JSON
+  - `<timestamp>-<slug>.json` full structured `CouncilRunResult`
+
 ## Determinism Notes
 
 - `prompt_payload_hash` is computed from canonical JSON payload passed to model.