ci: skip macos-15-intel smoke leg on prereleases

The macos-15-intel runner is the only smoke-test leg that cannot move
to Blacksmith (no Intel macOS option) and is the wall-clock floor of
every release. Beta releases trade Intel coverage for speed: stable
promotion to main still runs the full matrix and catches Intel-only
regressions before npm publish.

PR smoke (smoke-test-pr.yml passes prerelease: true) is also skipped
under this rule, accepting the trade-off that Intel-only issues will
surface at stable promotion rather than at PR time.

Refs CLI-1497.

Author: claude

.github/workflows/release-shared.yml

@@ -98,6 +98,11 @@ jobs:
 
   smoke-test:
     needs: build
+    # macos-15-intel is the slowest smoke leg and the only one not on
+    # Blacksmith (Blacksmith macOS is ARM-only). Skip it on prereleases
+    # (PR smoke + develop -> beta) so beta wall-clock isn't gated by it;
+    # stable releases on main still run the full matrix.
+    if: ${{ !(matrix.runner == 'macos-15-intel' && inputs.prerelease) }}
     strategy:
       fail-fast: false
       matrix: