BUG: Streaming test baselines stale for OpenSlide 3.4.1 (`itkOpenSlideTestStreaming`, `itkOpenSlideTestApproximateStreaming`)

Two streaming tests fail with enormous image-comparison errors when built against Ubuntu 22.04's OpenSlide 3.4.1; the stored baselines were produced by an older OpenSlide with a different JPEG decompression path. `main` reproduces (latest "Build, test, package" run on `main` is red).

Failing tests and magnitudes

| Test | ImageError |
|---|---|
| `itkOpenSlideTestApproximateStreaming` | 21,622,187 |
| `itkOpenSlideTestStreaming` | 18,887,606 |

Millions of differing pixels, mean error > 100 — this is a decode-path difference, not numeric drift. 7 of 9 tests pass, so the module itself is healthy.

Environment and reproduction

- Runner: `ubuntu-22.04`, system `libopenslide-dev 3.4.1+dfsg-5build1`.
- `main` reproduces: latest "Build, test, package" run on `main` is a failure (2026-04-23); prior `main` runs in Nov 2025 and Mar 2025 fail the same way.
- First surfaced by PR #37 (`COMP: Modernize CMake and update CI to v5.4.6 with OpenSlide system packages`, merged 2026-04-03), which is what first let CI actually build and run the test suite against a system OpenSlide.
- Stale baseline: `test/Input/CMU-1-level-1-stream-200.mha` (and its sibling streaming baseline).

Suggested fix

1. Build locally against OpenSlide 3.4.1 and run only the two streaming tests.
2. Capture the new outputs and confirm by eye that they are correct renderings (not a second wrong answer).
3. Upload the regenerated `.mha` baselines to ExternalData and update the content links.
**Note:** this repo migrated from `.md5` to `.cid` ExternalData tags in PR #38 (merged 2026-04-22), and PR #39 continues that migration and is **still open** — regenerate after #39 lands, and write `.cid` tags, not `.md5`.
4. Alternative if the decode path is expected to keep drifting across OpenSlide versions: give these two tests an explicit comparison tolerance / an allowed number of differing pixels rather than pinning a byte-exact baseline to one OpenSlide release.

Build against Ubuntu 22.04's OpenSlide 3.4.1 and run itkOpenSlideTestStreaming and itkOpenSlideTestApproximateStreaming. Inspect the existing test/Input/CMU-1-level-1-stream-200.mha and its sibling baseline, confirm regenerated outputs visually, then upload them to ExternalData and update the content links with .cid tags after PR #39 lands.

Written by the indexing model from the issue text.