FiducialCollection.estimatePose: ids/cornerss zip misaligns after ID filtering

Found 2026-08-03 while fixing the OpenCV 4/5 `ids` shape compat issue in the same method (see #44). `ImageFiducials.py`'s `FiducialCollection.estimatePose` does:

```python
cornerss = [
corners.T.squeeze()
for corners, id in zip(cornerss, ids)
if id in self._ids
]
ids = [id for corners, id in zip(cornerss, ids) if id in self._ids]
```

The second line's `zip(cornerss, ids)` pairs the already-filtered `cornerss` (reassigned on the line above) against the original, unfiltered `ids`. If any detected marker's ID isn't in `self._ids` (exactly the scenario the docstring calls out -- "filter the markers, useful if there are several ArUco boards in the scene"), the two lists have different lengths and `zip` silently pairs mismatched corners/ids from that point on. Only harmless when every detected marker happens to belong to this board (no actual filtering occurs), which is presumably why it hasn't been caught yet.

Fix

Compute the filtered `cornerss`/`ids` together in a single pass (e.g. one list comprehension producing tuples, then unzip), so both lists are always built from the same original, unfiltered pairing. Needs a test with multiple boards/extraneous marker IDs in view to catch a regression -- there's currently no coverage for the multi-board filtering case at all.

Start in ImageFiducials.py at FiducialCollection.estimatePose and inspect how detected corners and IDs are filtered. Add regression coverage for multiple boards or extraneous marker IDs, then verify that filtered corners and IDs remain aligned and the existing test suite passes.