…d is skipped (#8934)

When a PR only touches files outside the `node-changes` path filter (e.g. `meta/**`), `build-rolldown-ubuntu` is skipped and never uploads the native artifact — causing `vite-test-ubuntu` to fail unconditionally on the download step with `Artifact not found for name: rolldown-native-ubuntu-latest`.

## Change

Added the same `if` guard that already exists on the **Run Vite Tests** step to the **Download Native Rolldown Build** step in `vite-test-ubuntu`:

```yaml
- name: Download Native Rolldown Build
  if: ${{ needs.changes.outputs.node-changes == 'true' }}   # ← added
  uses: actions/download-artifact@...
  with:
    name: rolldown-native-ubuntu-latest
    path: ./packages
```

Other potentially affected jobs (`node-validation`, `vite-test-windows`) are already protected — `node-validation` by a job-level `if`, and `vite-test-windows` by its `github.ref_name == 'main'` gate.

<!-- START COPILOT ORIGINAL PROMPT -->

<details>

<summary>Original prompt</summary>

## Problem

The `vite-test-ubuntu` job (and potentially similar jobs) in `.github/workflows/ci.yml` fails when a PR only modifies files that don't match the `node-changes` path filter (e.g., doc-only changes under `meta/`).

Here's the chain of events:
1. A PR with no `node-changes` (e.g. only `meta/**` files changed) causes `needs.changes.outputs.node-changes == 'false'`.
2. `build-rolldown-ubuntu` calls `reusable-native-build.yml` with `changed: false`, which has `if: ${{ inputs.changed }}` — so the build job is **skipped** and **no artifact is uploaded**.
3. `vite-test-ubuntu` is still triggered (intentionally, for status checks), but it unconditionally runs the `Download Native Rolldown Build` step:
   ```yaml
   - name: Download Native Rolldown Build
     uses: actions/download-artifact@3e5f45b # v8.0.1
     with:
       name: rolldown-native-ubuntu-latest
       path: ./packages
   ```
   This fails with:
   > `Unable to download artifact(s): Artifact not found for name: rolldown-native-ubuntu-latest`

Note that the `Run Vite Tests` step already has the correct guard (`if: ${{ needs.changes.outputs.node-changes == 'true' }}`), but the **download step does not**.

## Fix

In `.github/workflows/ci.yml`, add `if: ${{ needs.changes.outputs.node-changes == 'true' }}` to **all** `Download Native Rolldown Build` steps that are gated on `build-rolldown-ubuntu` being skippable. Specifically, audit and fix:

- `vite-test-ubuntu` → `Download Native Rolldown Build` step (line ~200)
- `node-validation` → `Download Native Rolldown Build` step (line ~310)

Check if any other jobs in the same file have the same pattern (unconditional artifact download but the upstream build can be skipped) and fix those too.

The pattern to apply is consistent with how `Run Vite Tests` already works:
```yaml
- name: Download Native Rolldown Build
  if: ${{ needs.changes.outputs.node-changes == 'true' }}
  uses: actions/download-artifact@3e5f45b # v8.0.1
  with:
    name: rolldown-native-ubuntu-latest
    path: ./packages
```

The fix should be minimal �� only add the missing `if:` conditions to the download steps. Do not restructure jobs or change any other logic.

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: Do you know why the CI is failed? Don't write code https://github.com/rolldown/rolldown/actions/runs/23636641529/job/68847218961?pr=8931

Assistant: The CI failed due to a **missing artifact**. Here's the root cause:

> `Unable to download artifact(s): Artifact not found for name: rolldown-native-ubuntu-latest`

### What happened

This job tried to **download a pre-built native artifact** named `rolldown-native-ubuntu-latest` that was supposed to have been uploaded by an earlier job in the same workflow run (`run-id: 23636641529`). That artifact was never found.

### Likely reasons

1. **The upstream build job failed or was skipped** — The job that was supposed to compile and upload `rolldown-native-ubuntu-latest` either failed before uploading, was cancelled, or was skipped entirely. This is the most common cause.
2. **Artifact upload used an incompatible version** — The error message hints that a version mismatch between `upload-artifact` and `download-artifact` actions could cause this, though this is less likely if the workflow hasn't changed recently.
3. **The artifact expired** — Unlikely here since this is a fresh run, but artifacts do have a retention period.

### How to confirm

Check the other jobs in the same workflow run (`run-id: 23636641529`) — specifically the job responsible for building and uploading `rolldown-native-ubuntu-latest`. If that job failed or was skipped, it explains why this download job couldn't find the artifact.

User: Hot to fix it?

Assistant: Now I have the full picture. Here's a clear explanation:

---

## Root Cause

The failing job tried to download the `rolldown-native-ubuntu-latest` artifact, but **that artifact was never uploaded** — because the `build-rolldown-ubuntu` job was **skipped**.

Here's why it was skipped, tracing the logic:

### 1. `build-rolldown-ubuntu` is skipped when `node-changes == false`

In `reusable-native-build.yml` (line 18):
```yaml
if: ${{ inputs.changed }}
```
The build job only runs if `changed` is `true`. The `changed` input is passed as:
```yaml
changed: ${{ needs.changes.outputs.node-changes == 'true' }}
```

### 2. Your PR only modifies a Markdown doc file

PR #8931 only changes `meta/design/code-splitting.md`. Looking at the `node-changes` path filter in `ci.yml`:

```yaml
node-changes:
  - *rust-changes   # .github/workflows/**, crates/**, Cargo.toml, etc.
  - 'packages/**'
  - 'examples/**'
  - 'scripts/**'
  - 'package.json'
  - 'justfile'
  - 'rollup'
```

`meta/**` is **not included** in this list. So the `changes` job outputs `node-changes == false`, `build-rolldown-ubuntu` is skipped, **no artifact is uploaded**, and t...

</details>

<!-- START COPILOT CODING AGENT SUFFIX -->

*This pull request was created from Copilot chat.*
>

<!-- START COPILOT CODING AGENT TIPS -->
---

💬 Send tasks to Copilot coding agent from [Slack](https://gh.io/cca-slack-docs) and [Teams](https://gh.io/cca-teams-docs) to turn conversations into code. Copilot posts an update in your thread when it's finished.