ci: skip SPA build hook in jobs without bun

The setuptools build hook (setup.py) now runs build_ui.sh during every
'python -m build'/'make build'.  Three jobs build a wheel but have no bun/uv
to compile the SPA and never shipped one:
- package-testing (install/import variant tests) — workflow-level env
- ci-tests build-and-package (CI wheel artifact)
- dev-containers build (wheel for container scan)

Set ORB_SKIP_UI_BUILD=1 on their builds so they package a core-only wheel,
matching prior behaviour.  The release jobs (semantic-release, dev-pypi,
prod-release) set up bun and continue to build the full SPA.

Author: fgogolli

.github/workflows/ci-tests.yml

@@ -229,6 +229,10 @@ jobs:
         fail-on-cache-miss: false
 
     - name: Build package
+      # This job builds a wheel artifact for CI validation only and has no
+      # bun/uv to compile the SPA (it never shipped one).  Skip the UI build.
+      env:
+        ORB_SKIP_UI_BUILD: "1"
       run: make build
 
     - name: Upload build artifacts

.github/workflows/dev-containers.yml

@@ -127,6 +127,10 @@ jobs:
         fail-on-cache-miss: false
 
     - name: Build package wheel
+      # This job builds a wheel to scan in a container image and has no bun/uv
+      # to compile the SPA (it never shipped one).  Skip the UI build.
+      env:
+        ORB_SKIP_UI_BUILD: "1"
       run: make build
 
     - name: Build and scan container image

.github/workflows/package-testing.yml

@@ -17,6 +17,12 @@ on:
 permissions:
   contents: read
 
+# This workflow only tests install/import variants of the built wheel — it never
+# needs the Reflex SPA bundle, and its runners have no bun/uv to build one.  Skip
+# the SPA build hook (setup.py) for every `python -m build` in this file.
+env:
+  ORB_SKIP_UI_BUILD: "1"
+
 # Per-ref concurrency: prevents a rapid series of pushes to main from queuing
 # redundant package-testing runs.  Each ref can only have one run active at a
 # time; a newer push cancels the older in-progress run.