fix: prevent duplicate Windows ARM x64 R error message

Use errorOnce() instead of rethrowing WindowsArmX64RError to prevent
duplicate error messages when printCallRDiagnostics() calls
knitrCapabilities() again.

This scoped fix:
- Only affects WindowsArmX64RError handling
- Returns undefined like other knitrCapabilities errors
- Doesn't change general error handling in callR()

Author: cderv

src/core/knitr.ts

@@ -11,6 +11,7 @@ import { rBinaryPath, resourcePath } from "./resources.ts";
 import { readYamlFromString } from "./yaml.ts";
 import { coerce, satisfies } from "semver/mod.ts";
 import { debug } from "../deno_ral/log.ts";
+import { errorOnce } from "./log.ts";
 
 export interface KnitrCapabilities {
   versionMajor: number;
@@ -147,9 +148,10 @@ export async function knitrCapabilities(rBin: string | undefined) {
       return undefined;
     }
   } catch (e) {
-    // Rethrow x64-on-ARM errors - these have helpful messages
+    // Log x64-on-ARM errors once, then return undefined like other errors
     if (e instanceof WindowsArmX64RError) {
-      throw e;
+      errorOnce(e.message);
+      return undefined;
     }
     debug(
       `\n++ Error while running 'capabilities/knitr.R' ${