Add the analysis role's execution path: a two-phase orchestration
(per-scenario diagnosis gathered in parallel, then a synthesis pass)
that reads the existing campaign report aggregation plus capped failure
samples, validates the LLM's JSON against the report schema, and strips
fabricated run/scenario references before persisting. Results upsert one
row per campaign (generating/completed/failed) with the model config
snapshot; GET/POST /api/campaigns/{id}/analysis expose the state machine,
guarding non-terminal campaigns and missing analysis models with 400s.
Introduce ModelPurpose.ANALYSIS and a globally-unique is_analysis_default
marker on chat model configs so campaign analysis can resolve its model.
Service rejects disabled or non-chat configs; repo clears the previous
holder on set. Documented the analysis role in CONTEXT.md.
