fix(V_delta): correct truncated index.json superclasses (14 classes) + integrity test + all_ancestors map (review — do not merge)

[audriB]

What

schemas/V_delta/index.json carried a per-entry superclasses mirror that had dropped every non-base parent for 14 of 103 classes — e.g. neuron_extracellular missing app, tuningcurve_calc missing stimulus_tuningcurve, image_stack missing image_stack_parameters, the openminds_* missing openminds, stimulus_presentation missing app+epochid (full list in the commit).

Why it matters

Any consumer that resolves isa() / inheritance from index.json — rather than each class file's document_class.superclasses — gets silent false negatives (a neuron_extracellular not recognized as an app, a tuningcurve_calc not as a stimulus_tuningcurve, …). The per-class files are already correct; only the index mirror had drifted (it looks hand-maintained — no generator — and the test suite previously parametrized only V_beta/V_gamma, so nothing caught it).

What's in this PR

• schemas/V_delta/index.json — re-sync the 14 entries to their class files (only entries whose superclass set differed are touched; 31 insertions / 14 deletions, all inside superclasses arrays).
• tests/test_index_integrity.py — asserts index.superclasses == file superclasses for all 106 entries, that every referenced parent resolves, and that all_ancestors.json equals the transitive closure. First V_delta-tier test; verified it fails if an entry is re-truncated (213 pass).
• scripts/build_v_delta_aux.py — reproducible fixer (--fix-index) + builder of all_ancestors.json.
• schemas/V_delta/all_ancestors.json — a flattened transitive-closure inheritance map {class_name: [ancestors]} so consumers look up the full isa() chain without re-deriving it (e.g. tuningcurve_calc → app, base, calculator, stimulus_tuningcurve).

Review — do not merge.

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Found during a downstream audit of the web platform against schema-v2. Separate deferred item (not in this PR): stable/probe_location.json + stable/treatment.json ship the flat v1 shape while conversions/from_did_v1/*.md describe an ontology_term target marked drafted — happy to discuss whether to land that migration or mark the live files as intentionally-flat-pending-§2.4.

[audriB]

Closing — superseded by the V_epsilon anchor. This corrected a truncated-superclass defect in the V_delta index.json (14 classes) and added an all_ancestors map + integrity test. The platform is anchoring on V_epsilon, whose index.json is born-clean (0/187 superclass drift), so this V_delta-only fix is not on the critical path. Reopen if V_delta back-compat reads ever need a corrected index — the all_ancestors.json + tests/test_index_integrity.py remain on the branch (fix/v-delta-index-superclass-integrity) for reuse.