ci(semgrep): install with --ignore-installed (apt-managed PyJWT can't be uninstalled)

The runner's semgrep install failed trying to replace Debian's apt-managed PyJWT
("Cannot uninstall PyJWT ... RECORD file not found"). --ignore-installed installs
semgrep's deps fresh without uninstalling the apt copies, staying within the
runner's constraints (no setup-python, no container job).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -115,14 +115,17 @@ jobs:
     # Installed via the runner's preinstalled python3/pip — NOT `setup-python` (its Python
     # download failed on this runner) and NOT a job `container:` (this act_runner times out
     # pulling the base runner image for container jobs). `--break-system-packages` survives
-    # PEP-668; pip drops `semgrep` on PATH. Verified locally: install + scan run clean.
+    # PEP-668; pip drops `semgrep` on PATH. `--ignore-installed` is required because some of
+    # semgrep's deps (e.g. PyJWT) are already present as apt-managed packages, which pip cannot
+    # uninstall ("RECORD file not found") — this flag installs fresh without uninstalling, so it
+    # never touches the Debian copies. Don't drop it.
     # ponytail: report-only for now (no `--error`, so the job stays green while the initial
     # findings are triaged); flip to `--error` to make it a blocking gate. See WP-30.
     runs-on: ubuntu-latest
     timeout-minutes: 15
     steps:
       - uses: actions/checkout@v4
-      - run: python3 -m pip install --break-system-packages semgrep
+      - run: python3 -m pip install --break-system-packages --ignore-installed semgrep
       # p/default = curated cross-language security (covers JS/TS); p/csharp = the backend.
       # Anonymous registry fetch; --metrics=off disables telemetry (not `auto`, which uploads
       # project metadata).