fix: Linux build — remove hardcoded arch from electron-builder config

electron-builder.yml listed `arch: [x64, arm64]` on every Linux target,
causing both architectures to build on each CI job regardless of the
--x64/--arm64 CLI flag. This made:
- x64 job produce arm64 artifacts (failing verification)
- arm64 job attempt x64 native module rebuild (zlib-sync -m64 fails on arm)

Fix: remove arch arrays from linux.target entries, let CLI flags control
which architecture to build per job.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 7418

electron-builder.yml

@@ -83,10 +83,10 @@ linux:
       Comment: A native desktop GUI for Claude Code
       Categories: Development;IDE;
       StartupWMClass: codepilot
+  # arch is NOT specified here — controlled by CI via --x64 / --arm64 CLI flags.
+  # Listing both arches here causes electron-builder to build both on every job,
+  # which fails when cross-compiling native modules (zlib-sync -m64 on arm64).
   target:
-    - target: AppImage
-      arch: [x64, arm64]
-    - target: deb
-      arch: [x64, arm64]
-    - target: rpm
-      arch: [x64, arm64]
+    - AppImage
+    - deb
+    - rpm