fix(ci): pr_test_summary reports '0 passed' when all test jobs are skipped

[ramakrishnap-nv]

Problem

When a PR only touches files that don't trigger any test jobs (e.g. pure C++ changes where Python/wheel/server jobs are skipped), the CI Test Summary bot comment reads:

✅ All 0 test job(s) passed.

This is misleading — no tests ran, but the message implies a clean pass.

Root Cause

In `ci/utils/pr_test_summary.py`, `_build_body()` has three branches:

• `failed` → show failures
• `cancelled` → show passed/skipped/cancelled counts
• `else` → `"✅ All {len(passed)} test job(s) passed."`

When all test jobs are skipped (`passed=[]`, `skipped=[N jobs]`, `failed=[]`, `cancelled=[]`), it falls into the `else` branch and emits `"✅ All 0 test job(s) passed."`

Fix

Add an explicit branch for the all-skipped case:

```python
elif not passed:
lines.append(f"⏭️ All {len(skipped)} test job(s) skipped.")
else:
msg = f"✅ All {len(passed)} test job(s) passed."
if skipped:
msg += f" ({len(skipped)} skipped)"
lines.append(msg)
```

The fix was committed directly to `main` (commit `8973c65d`) — this should have gone through a PR. A follow-up PR should be opened to formally track the change and ensure it goes through review.

Follow-up

• Open a PR against `main` with the fix from commit `8973c65d`
• Verify the bot comment updates correctly on the next PR run where all jobs are skipped