fix(build): exclude skill stub sources from packages

config/electron-builder.config.cjs

@@ -66,9 +66,10 @@ module.exports = {
     '!mobile{,/**/*}',
     '!native{,/**/*}',
     '!skills{,/**/*}',
-    // Why: authoritative guide markdown is compiled into out/cli; shipping the
-    // authoring sources too would duplicate content without a runtime consumer.
+    // Why: guide/stub authoring sources are compiled into runtime artifacts; shipping
+    // either source tree would duplicate content without a runtime consumer.
     '!skill-guides{,/**/*}',
+    '!skill-stubs{,/**/*}',
     '!tests{,/**/*}',
     // Why: pr-evidence/ is a local e2e screenshot output (ORCA_CAPTURE_EVIDENCE);
     // it is gitignored, but exclude it defensively so a stray local capture at

config/scripts/electron-builder-config.test.mjs

@@ -29,6 +29,7 @@ describe('electron-builder config', () => {
         '!native{,/**/*}',
         '!skills{,/**/*}',
         '!skill-guides{,/**/*}',
+        '!skill-stubs{,/**/*}',
         '!resources/skills/**',
         '!tests{,/**/*}',
         '!pr-evidence{,/**/*}',