docs: 📝 fix three cross-page anchors that never resolved

The links carried a double dash where mkdocs slugifies "+" and "&" down to
a single one, so every one of them landed at the top of the target page
instead of the intended section. Caught by a --strict build.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: lguerard

docs/guide/label_relations.md

@@ -24,7 +24,7 @@ table[2]
 `table` only contains matched `a` labels (nuclei with at least one
 overlapping voxel in `cells`) — unmatched labels and full per-`b` coverage
 need a bit more bookkeeping (the [cluster workflow's `run_multi.py`
-script](snakemake.md#one-command-multiple-segmentations--relations) does
+script](snakemake.md#one-command-multiple-segmentations-relations) does
 this for you and writes it as a two-sheet workbook).
 
 Save it as a table yourself:
@@ -41,4 +41,4 @@ with open("nuclei_to_cell.csv", "w", newline="") as f:
 
 On the cluster, producing the two label stores in the first place is a
 matter of running the workflow twice against the same `work_dir` — see
-[Running two segmentations](snakemake.md#running-two-segmentations-eg-nuclei--cytoplasm).
+[Running two segmentations](snakemake.md#running-two-segmentations-eg-nuclei-cytoplasm).

docs/guide/measurements.md

@@ -10,7 +10,7 @@ is built for this — its "Measure" dock widget computes area/centroid/intensity
 stats directly off a Labels layer's dask/zarr-backed array, out-of-core, and
 scales with chunk count rather than object count. It's the best fit for
 measuring *every* object in a store this size, not just a cropped region —
-see [View image + labels in napari](ome_zarr_napari.md#view-image--labels-in-napari).
+see [View image + labels in napari](ome_zarr_napari.md#view-image-labels-in-napari).
 Bundled in `patchworks[napari]`.
 
 For interactively inspecting individual cells by clicking in the viewer (not