ci(tests): pin setup-uv to a concrete version

Run 4's `Tests / test` and `Tests / e2e` both failed at the
`Install uv` step with:

  No (valid) GitHub token provided. Falling back to anonymous.
  ::error::API rate limit exceeded for 5.78.80.188.

`astral-sh/setup-uv` queries api.github.com to resolve the latest
uv release. Our act_runner's egress IP (5.78.80.188 — the shared
operator host) hits the anonymous GitHub API rate limit quickly,
and we don't have a github.com PAT injected as GITHUB_TOKEN
post-suspension.

Per setup-uv's docs, requesting a concrete version like "0.11.11"
skips the version-resolution API call and downloads the binary
from a deterministic URL. No GitHub credentials needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/tests.yml

@@ -33,6 +33,11 @@ jobs:
 
       - name: Install uv
         uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86  # v5
+        with:
+          # Pin a concrete version so the action skips the api.github.com
+          # release-resolution call. The shared act_runner egress IP is
+          # rate-limited on anonymous GitHub API after the org suspension.
+          version: "0.11.11"
 
       - name: Set up Python 3.11
         run: uv python install 3.11
@@ -62,6 +67,11 @@ jobs:
 
       - name: Install uv
         uses: astral-sh/setup-uv@d4b2f3b6ecc6e67c4457f6d3e41ec42d3d0fcb86  # v5
+        with:
+          # Pin a concrete version so the action skips the api.github.com
+          # release-resolution call. The shared act_runner egress IP is
+          # rate-limited on anonymous GitHub API after the org suspension.
+          version: "0.11.11"
 
       - name: Set up Python 3.11
         run: uv python install 3.11