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

src/councils/types.ts

@@ -166,6 +166,7 @@ export const councilTraceEventSchema = z.object({
     inputTokens: z.number().int().min(0),
     outputTokens: z.number().int().min(0),
   }).strict().optional(),
+  latency_ms: z.number().int().min(0).optional(),
   dropped_reason: droppedReasonSchema.optional(),
   validation_failure: validationFailureReasonSchema.optional(),
 }).strict();