Validate OME-Zarr 0.5 rendering and client behavior

[uermel]

Parent epic: #13

Goal

Prove and, where evidence requires, repair client behavior for OME-Zarr 0.5 / Zarr v3 while retaining parity for legacy data and existing viewer interactions.

Scope

• Test the exact current @idetik/core 0.35.0 / Zarrita 0.7.3 lock first.
• Add component tests for image-source creation, loading/error states, contrast initialization, layer disposal, and segmentation overlays.
• Add real-browser tests through the production-shaped HTTP proxy for every fixture category.
• Validate OME-Zarr 0.4 and 0.5 metadata discovery and Zarr v2/v3 arrays.
• Validate canonical sharding_indexed, numcodecs.shuffle, and Zstandard decoding.
• Assert decoded checksums/values, shapes, dtypes, level selection, channel selection, contrast, and axial/coronal/sagittal orientation.
• Validate segmentation labels, color/opacity, pick overlays, and coordinate alignment.
• Assert expected HEAD and Range network behavior for sharded reads and detect unexpected full-shard transfers.
• Cover abort, loading, error, and empty states with no uncaught browser errors.
• Upgrade Idetik/Zarrita only if a minimal fixture-backed reproduction proves the locked versions insufficient, and isolate that change for review.

Acceptance criteria

• OME-Zarr 0.4 / Zarr v2 and OME-Zarr 0.5 / Zarr v3 render in one client build.
• Canonical integer and shuffled floating-point data decode to manifest checksums.
• Multiscale levels, channels, coordinate transforms, orientations, and contrast match expectations.
• Segmentation and pick overlays align and preserve existing interaction behavior.
• Sharded browser reads use bounded range requests.
• Browser tests report no uncaught errors, codec warnings, or runaway request loops.
• Any reader dependency upgrade includes the minimal reproduction and a reviewed lock-file delta.

Out of scope

• Replacing Idetik/Zarrita without a demonstrated blocker.
• Implementing backend retry logic in the browser.
• Changing the core storage layout or codecs.

[uermel]

PR #19 validates the locked Idetik/Zarrita reader against OME-Zarr 0.4/Zarr v2 numeric and nonnumeric paths plus OME-Zarr 0.5/Zarr v3 unsharded, canonical sharded integer, shuffled floating-point, invalid-metadata, and truncated-shard cases. Node 20.19 and 22 pass, and sharded reads are behavior-checked for HEAD plus bounded Range traffic. Broader real-browser/UI interaction coverage remains open.