feat(deck-multi): migrate deck_multi chart to the v1 chart data API

[rusackas]

SUMMARY

Tier 4 of #41714 (targets remove-legacy-viz-pipeline): migrate deck.gl Multiple Layers (deck_multi) off explore_json — the last useLegacyApi chart, and the last holdout in the deck.gl preset migration.

deck_multi depended on explore_json twice: the container query (whose viz.py class fetched every sub-slice server-side just to hand back metadata and merged features) and each per-layer data fetch. Both move client-side:

• New Multi/buildQuery.ts returns an empty queries list — the legacy DeckGLMultiLayer.query_obj was empty too; a new backend unit test pins that ChartDataQueryContextSchema accepts that shape.
• Multi.tsx fetches sub-slice metadata via GET /api/v1/chart/<id> (bounded by deck_slices), and loads each layer through its own registered buildQuery → POST /api/v1/chart/data → registered transformProps, whose output payload is exactly what the layer generators consume. Legacy container payloads (cached) still short-circuit the metadata fetch.
• Layer-scoped dashboard filtering (layer_filter_scope/filter_data_mapping), dashboardId and parent_slice_id propagation are unchanged — tests updated to assert them on the v1 POST payloads.
• Known minor behavior notes: initial autozoom falls back to the saved viewport when no pre-merged container features exist (bounds previously came from the container payload), and dashboard filter badges no longer aggregate child-layer applied-filter metadata (the legacy container merged it server-side).

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

No visual change in layer rendering; see autozoom note above.

TESTING INSTRUCTIONS

• npm run test -- plugins/preset-chart-deckgl/src/Multi — 30 tests pass (layer loading via registries, dashboardId/parent_slice_id propagation on POST payloads, layer visibility filtering, viewport handling).
• pytest tests/unit_tests/charts/data/test_empty_query_context.py — empty-queries context accepted.
• Manual: open a saved deck.gl Multiple Layers chart; network tab shows one POST /api/v1/chart/data per layer (no /superset/explore_json/); layer-scoped dashboard filters behave as before.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
• Introduces new feature or API
• Removes existing feature or API

🤖 Generated with Claude Code

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[codecov]

Codecov Report

❌ Patch coverage is 57.69231% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.68%. Comparing base (907b18a) to head (f15137d).
⚠️ Report is 7 commits behind head on remove-legacy-viz-pipeline.

Files with missing lines	Patch %	Lines
...nd/plugins/preset-chart-deckgl/src/Multi/Multi.tsx	61.22%	19 Missing ⚠️
...lugins/preset-chart-deckgl/src/Multi/buildQuery.ts	0.00%	2 Missing ⚠️
...end/plugins/preset-chart-deckgl/src/Multi/index.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                      Coverage Diff                       @@
##           remove-legacy-viz-pipeline   #41730      +/-   ##
==============================================================
+ Coverage                       63.91%   64.68%   +0.76%     
==============================================================
  Files                            2697     2698       +1     
  Lines                          148702   148734      +32     
  Branches                        34331    34339       +8     
==============================================================
+ Hits                            95040    96204    +1164     
+ Misses                          51912    50768    -1144     
- Partials                         1750     1762      +12     

Flag	Coverage Δ
hive	39.19% <ø> (ø)
javascript	69.48% <57.69%> (-0.04%)	⬇️
mysql	57.84% <ø> (?)
postgres	57.91% <ø> (?)
presto	40.73% <ø> (ø)
python	59.30% <ø> (+1.65%)	⬆️
sqlite	57.48% <ø> (ø)
unit	100.00% <ø> (?)

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