fix(news): restore unreachable throw to satisfy TS narrowing

#432's "remove dead code" change deleted a post-loop throw that was
unreachable at runtime but required for TypeScript to narrow the
return type. Without it, the for-loop's normal exit path makes the
function signature `Promise<{...} | undefined>`, which fails to match
the MCP tool registration parameter type.

Restored the throw with a comment explaining why it must stay even
though it's "dead." Build clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: whoabuddy

src/tools/news.tools.ts

@@ -833,7 +833,13 @@ Fields:
           );
         }
 
-
+        // Unreachable at runtime: the for-loop always exits via return (success)
+        // or throw (non-retryable failure or final retry exhausted). Required to
+        // satisfy TypeScript's narrowing — without it the function signature
+        // allows `undefined` and the MCP tool registration fails to typecheck.
+        throw new Error(
+          `Signal filing failed after ${MAX_ATTEMPTS} attempts. Last error: ${lastError}`
+        );
       } catch (error) {
         return createErrorResponse(error);
       }