fix(openapi): declare the body-cap 413 and the outbound-screen 502 of a briefing generation

Both have always been answered; neither was declared. The parity walk now
checks them against the contract instead of skipping it.

src/lib/openapi/routes/insights/paths.ts

@@ -276,6 +276,15 @@ export const insightsPaths: NonNullable<ZodOpenApiObject["paths"]> = {
             "Every provider in the chain failed for a reason that is not a rate limit — auth, timeout or an upstream 5xx. A dated failure marker is written, so the read GET reports the briefing as held rather than fresh. Also: the `briefing` capability could not be resolved (`meta.errorCode` = `ai.unavailable`, `meta.reason` = `check_failed`); nothing was generated.",
           content: { "application/json": { schema: errorEnvelope } },
         },
+        "413": {
+          description: "The request body is over 16 KB. Nothing was generated.",
+          content: { "application/json": { schema: errorEnvelope } },
+        },
+        "502": {
+          description:
+            "The generated briefing did not pass the outbound safety screen and was discarded (`meta.errorCode` = `insights.generate.outboundScreened`). Regenerating may succeed.",
+          content: { "application/json": { schema: errorEnvelope } },
+        },
         "401": stdResponses["401"],
       },
     },