ci: bootstrap pin -> 2026.7.30.3 (released, mirrored, indexed, install-verified)

Release v2026.7.30.3 is live on all four platforms, mirrored to xlings-res on
both GitHub and GitCode (8/8 assets verified by real GET, sha256 cross-checked
against the upstream sidecars), and served by xim-pkgindex (#457). A clean-room
`xlings install mcpp@2026.7.30.3` installs and runs it.

Author: Sunrisepeak

.github/workflows/ci-fresh-install.yml

@@ -40,7 +40,7 @@ concurrency:
 # fails with `version not found` instead of silently testing an older
 # binary. Bump together with the .xlings.json workspace pin at release.
 env:
-  MCPP_PIN: '2026.7.30.2'
+  MCPP_PIN: '2026.7.30.3'
 
 jobs:
   # ──────────────────────────────────────────────────────────────────

.xlings.json

@@ -1,5 +1,5 @@
 {
   "workspace": {
-    "mcpp": "2026.7.30.2"
+    "mcpp": "2026.7.30.3"
   }
 }