chore(voyage): release v5.8.0 - SKAL-1·4b offline gold-scored output eval

Version sync 5.7.1 -> 5.8.0 across plugin.json, package.json,
package-lock.json, README badge, and CHANGELOG top entry (guarded by
doc-consistency.test.mjs). Suite 822 (820/0/2).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BJQYC5vpkJWxndS55vQQZ6

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "voyage",
-  "version": "5.7.1",
+  "version": "5.8.0",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "voyage",
-      "version": "5.7.1",
+      "version": "5.8.0",
       "license": "MIT",
       "engines": {
         "node": ">=18"