CODAP-1469: make residual-plot points marquee-selectable

[kswenson]

Summary

Adds marquee (drag-rectangle) selection to the residual plot, alongside the
existing click selection. Fixes CODAP-1469.

• Dragging on the residual strip selects the residual points inside the rectangle;
  selection updates dynamically while dragging, and Shift adds to the current
  selection.
• Selection is confined to the residual strip (separate zone) — the upper-plot
  marquee and the map marquee are unchanged. A rectangle spanning both the main
  Y-axis space and the residual space has no coherent meaning, so the two zones
  stay independent.
• A click (no drag) still deselects all cases, as before.

Implementation notes

• Residual points are hand-drawn SVG circles that the point renderer doesn't
  track, so the shared Background marquee (which hit-tests the renderer's
  R-tree) can't see them. The new useResidualMarquee hook builds its own
  R-tree from the residual positions on pointerdown and selects via the same
  delta hit-testing — the R-tree is built up front to stay efficient with large
  datasets (one residual point per case).
• Refactor: the residual rendering/sync code was extracted out of
  scatter-plot.tsx into a useResidualPlot hook, and Background's
  getCasesForDelta was moved into data-display-utils.ts so both marquees
  share it.

Reviewer notes

This PR is a mix of new logic and mechanical moves — the commit history is
structured so each is reviewable on its own.

New code (warrants closer review):

• use-residual-marquee.ts — the new drag-select behavior: R-tree build,
  delta hit-testing, dynamic/Shift selection, the pointer→plot-area coordinate
  conversion, and the click-vs-drag threshold that preserves click-to-deselect.
• residual-marquee-utils.ts — new pure helpers (buildResidualPositions,
  clampRectToLowerRegion) + their unit tests.
• scatter-plot.tsx — the new bits only: the useResidualMarquee call and
  the residual hit-rect's onPointerDown/onClick wiring (the rest of the diff
  in this file is the extraction below).
• use-marquee-state.ts + the MarqueeStateContext provider in graph.tsx —
  new, but trivial context plumbing.
• bivariate-adornments.spec.ts — new Cypress test.
• the getCasesForDelta unit test in data-display-utils.test.ts.

Moved / mechanical (lighter review):

• use-residual-plot.ts — a behavior-preserving extraction of the residual
  rendering/sync code out of scatter-plot.tsx (no logic changes; the guards
  and untracked wrapping were moved verbatim). Most of the scatter-plot.tsx
  deletions are the other side of this move.
• getCasesForDelta moved from background.tsx into data-display-utils.ts;
  background.tsx just imports it now.
• the graph.tsx reindent commit is whitespace only (JSX nested under the new
  provider).

Testing

• Unit tests for the extracted getCasesForDelta and the pure residual-marquee
  geometry helpers.
• Cypress e2e: drag-selecting residual points on the strip (plus the existing
  click select/deselect coverage).

[codecov]

Codecov Report

❌ Patch coverage is 94.69027% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.79%. Comparing base (6fc144a) to head (5a084d9).

Files with missing lines	Patch %	Lines
...ents/graph/plots/scatter-plot/use-residual-plot.ts	94.28%	6 Missing ⚠️
...s/graph/plots/scatter-plot/use-residual-marquee.ts	95.00%	4 Missing ⚠️
.../components/data-display/components/background.tsx	33.33%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2677       +/-   ##
===========================================
+ Coverage   72.82%   87.79%   +14.96%     
===========================================
  Files         810      814        +4     
  Lines       46933    47045      +112     
  Branches    11999    12012       +13     
===========================================
+ Hits        34179    41303     +7124     
+ Misses      12721     5726     -6995     
+ Partials       33       16       -17     

Flag	Coverage Δ
cypress	69.69% <94.00%> (+31.53%)	⬆️
jest	62.64% <22.56%> (-0.02%)	⬇️

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[cypress]

codap-v3    Run #12092

Run Properties:   Passed #12092  •  5a084d9f9f: null

Project	codap-v3
Branch Review	CODAP-1469-residual-plot-marquee-selection
Run status	Passed #12092
Run duration	08m 37s
Commit	5a084d9f9f: null
Committer	null
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	1
Pending	82
Skipped	0
Passing	383
View all changes introduced in this branch ↗︎

[Copilot]

Pull request overview

Adds residual-strip marquee (drag-rectangle) selection to the scatter plot’s residual plot, sharing marquee state/logic with existing background selection and preserving click-to-deselect behavior (CODAP-1469).

Changes:

• Introduces a residual-specific marquee implementation (useResidualMarquee) that builds an R-tree from residual point positions on pointerdown and updates selection dynamically while dragging.
• Refactors residual plot rendering/sync/selection styling into useResidualPlot, and shares delta hit-testing via getCasesForDelta moved into data-display-utils.ts.
• Adds MarqueeState context plumbing and new unit/Cypress coverage for residual marquee behavior and helper utilities.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
v3/src/components/graph/plots/scatter-plot/use-residual-plot.ts	New hook encapsulating residual plot rendering, axis/split-layout sync, and selection restyling.
v3/src/components/graph/plots/scatter-plot/use-residual-marquee.ts	New residual-strip-only marquee selection logic (R-tree build + delta hit-testing).
v3/src/components/graph/plots/scatter-plot/scatter-plot.tsx	Wires in useResidualPlot + useResidualMarquee and updates residual background hit-rect handlers.
v3/src/components/graph/plots/scatter-plot/residual-marquee-utils.ts	Pure helpers for residual point screen positions and lower-region rect clamping.
v3/src/components/graph/plots/scatter-plot/residual-marquee-utils.test.ts	Unit tests for residual marquee helper utilities.
v3/src/components/graph/components/graph.tsx	Provides MarqueeState via context in addition to existing prop threading.
v3/src/components/data-display/hooks/use-marquee-state.ts	Adds MarqueeStateContext + hook for descendant access.
v3/src/components/data-display/data-display-utils.ts	Moves/exports getCasesForDelta and related types for shared marquee delta selection.
v3/src/components/data-display/data-display-utils.test.ts	Adds unit tests for getCasesForDelta.
v3/src/components/data-display/components/background.tsx	Uses shared getCasesForDelta and shared CaseObject/RTree types.
v3/cypress/e2e/bivariate-adornments.spec.ts	Adds e2e coverage for residual-strip marquee selection.

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[Copilot]

Pull request overview

Copilot reviewed 11 out of 11 changed files in this pull request and generated 2 comments.