getCloudDatasetIdForLocalDataset is dead for every real dataset; port dataset.isInCloud() #95

Part of #90 (PR #61 catch-up). Items M3 and one of the found-while-porting fixes. Both verified against main today.

1. getCloudDatasetIdForLocalDataset always returns ("", None)

src/ndi/cloud/internal.py:60 does:

try:
    db = dataset.database
    ...
except Exception:
    pass
return "", None

ndi_dataset has no database attribute. Its only properties are reference and cloud_client; the database lives on the backing session (dataset._session._database), and the class exposes it only through the database_add / database_search / database_rm methods. So dataset.database raises AttributeError on every call, the bare except Exception: pass swallows it, and the function reports "never uploaded" for every dataset that has in fact been uploaded.

This is not cosmetic: src/ndi/cloud/orchestration.py:397-403 auto-detects the cloud id through this function, so the auto-detect path is permanently broken. It went unnoticed because every test mocks the function out.

Fix: accept either shape — a database attribute when present, otherwise dataset._session._database — and return early with a debug log rather than swallowing. Drop the bare except Exception: pass; it is what hid this for as long as it did. Reference: commit 1833a09.

Test: the regression test must use a real ndi_dataset, not a mock. Mocking is precisely what let this ship.

2. dataset.isInCloud() is not ported

MATLAB dataset.m:260-296 (PR #859). No Python equivalent exists — grep -rn "isInCloud\|is_in_cloud" src/ returns nothing.

It answers the same question as item 1 and must agree with it, so the two belong in one change: implement isInCloud() on ndi_dataset over the same dataset_remote lookup, and cross-reference them in the docstrings.

Test: isInCloud() makes no network call, and the test should measure that rather than assert it in prose — PR #61 commit 0e1738b exists solely because the first version of that test claimed no-network without checking. Reference commits: 490412e, 0e1738b.

Effort

Small — both changes are contained in src/ndi/cloud/internal.py and src/ndi/dataset/_dataset.py, with no dependency on the file-services rework that made other PR #61 patches unportable.