fix(CI): set WORKSPACE_ID env var for test job

PR #29 introduced WORKSPACE_ID validation at module import time
(platform_auth.py). The CI environment did not set WORKSPACE_ID,
causing 8 failures + 13 errors on every main push. Add a dummy
CI-only value so imports succeed without affecting real workspaces.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -8,6 +8,10 @@ on:
 jobs:
   test:
     runs-on: ubuntu-latest
+    env:
+      # Required by platform_auth.validate_workspace_id() (PR #29 / issue #14).
+      # Valid format: lowercase alphanumeric + hyphens (matches UUIDs and org IDs).
+      WORKSPACE_ID: ci-test-workspace
     steps:
       - uses: actions/checkout@v4