chore: bootstrap from 2026.8.1.1

The bootstrap pin is the starting point of self-hosting, not a copy of the
version being built, so it moves only after the release is published, mirrored
and merged into xim-pkgindex — all three now verified:

  - both hosts serve all four platforms, byte-identical sizes
  - sha256 recomputed from each payload (not read from the sidecar) matches
    what xim-pkgindex#467 records: 3ff4e68 / 40a9cee / faa2e86 / e81bb42
  - clean-room XLINGS_HOME install of mcpp@2026.8.1.1 succeeds and reports
    2026.8.1.1 (took 4 attempts over ~7 min — the documented index-CDN
    propagation lag, not a failure)
  - the released binary passes 178_test_observability end to end, so the
    feature this release exists for is verified on the artifact users get,
    not only on a local build

A green CI round on the bumped pin is the direct proof that 2026.8.1.1 can
build mcpp itself on every platform.

Author: Sunrisepeak

.xlings.json

@@ -1,5 +1,5 @@
 {
   "workspace": {
-    "mcpp": "2026.7.31.1"
+    "mcpp": "2026.8.1.1"
   }
 }