feat(partition): migrate partition chart to v1 chart data API

[rusackas]

SUMMARY

Tier 4 of #41714 (targets remove-legacy-viz-pipeline): migrate the Partition Chart (partition) off explore_json onto /api/v1/chart/data. This was the largest viz.py transform left.

• New buildQuery.ts mirroring PartitionViz.query_obj: grouped query, is_timeseries only for time-based options, legacy sort-metric append/orderby.
• transformData ports the full get_data dispatch:
  • not_time/agg_sum/agg_mean → levels_for + nest_values (summed/averaged hierarchy, dim-path names at deeper levels, sorted group indexes);
  • time_series → same nesting with the timestamp prepended as the first level;
  • point_diff/point_factor/point_percent → levels_for_diff (last vs first time grain, pandas fill_value=0 semantics for grouped rows, plain arithmetic at the top level);
  • adv_anal → levels_for_time + nest_procs (per-timestamp pivot summed with missing combos filled as 0, rolling mean/sum/std/cumsum with min_periods trimming, contribution row-normalization per level).
• useLegacyApi: true removed (and the "Legacy" tag dropped).
• No DB migration: viz_type unchanged; legacy granularity_sqla/time_range handled by extractExtras.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

No visual change — same renderer, same data shape, different endpoint.

TESTING INSTRUCTIONS

• npm run test -- plugins/legacy-plugin-chart-partition — 13 Jest tests covering every time-series option (hierarchy shape and values, mean vs sum, point comparisons incl. missing-side fill, timestamp-first nesting, period analysis with cumsum and contribution, groupby validation, query shapes).
• Manual: open a saved Partition Chart in each time-series mode; network tab shows POST /api/v1/chart/data; rendering identical.

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 87.12871% with 26 lines in your changes missing coverage. Please review.
✅ Project coverage is 63.94%. Comparing base (907b18a) to head (a6f060f).
⚠️ Report is 4 commits behind head on remove-legacy-viz-pipeline.

Files with missing lines	Patch %	Lines
...legacy-plugin-chart-partition/src/transformData.ts	89.44%	19 Missing ⚠️
...egacy-plugin-chart-partition/src/transformProps.ts	0.00%	6 Missing ⚠️
...plugins/legacy-plugin-chart-partition/src/index.ts	0.00%	1 Missing ⚠️

Additional details and impacted files

@@                      Coverage Diff                       @@
##           remove-legacy-viz-pipeline   #41729      +/-   ##
==============================================================
+ Coverage                       63.91%   63.94%   +0.03%     
==============================================================
  Files                            2697     2699       +2     
  Lines                          148702   148904     +202     
  Branches                        34331    34400      +69     
==============================================================
+ Hits                            95040    95216     +176     
- Misses                          51912    51938      +26     
  Partials                         1750     1750              

Flag	Coverage Δ
javascript	69.56% <87.12%> (+0.04%)	⬆️

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