chore: release v1.7.115-alpha

Signed OTA manifest (release root verified). Also: create-release-manifest
tarball perms check made SIGPIPE-proof so releases cut on macOS too.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/create-release-manifest.sh

@@ -142,7 +142,7 @@ if [ -z "$FRONTEND_ARCHIVE" ]; then
         # SIGPIPE-safe: use awk to read only the first line and exit,
         # then terminate the tar pipeline explicitly so `pipefail`+SIGPIPE
         # don't kill the whole `set -euo pipefail` script.
-        root_mode=$(tar tvzf "$FRONTEND_ARCHIVE" 2>/dev/null | awk 'NR==1{print $1; exit}')
+        root_mode=$({ tar tvzf "$FRONTEND_ARCHIVE" 2>/dev/null || true; } | awk 'NR==1{print $1; exit}')
         case "$root_mode" in
             drwxr-xr-x|drwxr-x*x*)
                 echo "  Tarball root perms OK: $root_mode"