Plan viewer: minimap resize, double-click zoom and coloured edges (#4580)

[erikdarlingdata]

Fixes #4580. Builds on #4596. Part of #4511.

Why

Part 1 (#4596) added the plan viewer's minimap panel but left three items for this pass, per PerformanceStudio's PlanViewerControl.Minimap.cs: a resizable panel with its size remembered across plans, double-click on a minimap node to zoom and select it, and accuracy-ratio coloured minimap edges (using the PlanEdgeColour helper from #4586, which is already on dev).

What changes

• The minimap panel gets a header with a resize grip (top-left corner, since the panel is pinned bottom-right) and a close button. Dragging the grip resizes the panel between 160px and 500px on each axis, matching PerformanceStudio's bounds. The size is kept in a field that survives across plans and control instances (a static field, mirroring PerformanceStudio), so reopening the minimap on a different plan keeps the size the user last set.
• Double-clicking a node in the minimap zooms the main canvas so that node takes about a third of the viewport, scrolls to center it, and selects it (same as clicking it directly on the main canvas). A single click anywhere in the minimap still centers the viewport there, whether or not it lands on a node.
• Minimap edges are coloured by the same actual/estimated row-count ratio as the main canvas' edges, through the existing PlanEdgeColour helper and the same six-brush set the main canvas already defines — no new colours were introduced.
• The pure geometry (the resize clamp, the zoom-to-node level and center offset, and node hit-testing for double-click) lives in MinimapLayout, alongside the geometry part 1 added. The WPF code-behind only wires these numbers to mouse events and the existing shapes.
• Lite: gets this too (shared control — no separate work needed).

Test plan

Pins added to Darling/Darling.Tests/Viewer4580Tests.cs (existing file from part 1; new members are new on this branch, so the RED for them is a compile failure on part 1's b3317c250):

• ClampPanelSize: clamps to 160-500.
• ResizeFromDrag: subtracts the drag delta from the starting size (growing toward the pinned corner), clamped to bounds.
• GetZoomToNodeLevel: fits a node to about a third of the viewport, clamped to the zoom range, returns the minimum zoom when the viewport or node has no size.
• GetNodeCenterOffset: centers a node in the viewport, clamped to zero near the edges.
• FindNodeAt: returns the node whose minimap rectangle contains a point, or null.

Runtime mutation (behavioural RED): flipped ResizeFromDrag's subtraction to addition — ResizeFromDrag_SubtractsDeltaFromStartSize_ClampedToBounds and ResizeFromDrag_ClampsBelowMinAndAboveMax both failed (Darling.Tests Total: 26, Failed: 2); reverted, rebuilt, all 26 green again.

Commands run (macOS, in-process xunit v3 runner, Microsoft.WindowsDesktop.App stripped from the runtimeconfig):

dotnet build Darling/Darling.Tests/Darling.Tests.csproj -c Release -p:EnableWindowsTargeting=true
dotnet build PerformanceMonitor.Ui/PerformanceMonitor.Ui.csproj -c Release -p:EnableWindowsTargeting=true
dotnet build Lite/PerformanceMonitorLite.csproj -c Release -p:EnableWindowsTargeting=true
dotnet build Darling/PerformanceMonitor.Darling.Viewer/PerformanceMonitor.Darling.Viewer.csproj -c Release -p:EnableWindowsTargeting=true
dotnet Darling.Tests.dll -class Darling.Tests.Viewer4580Tests \
  -class Darling.Tests.CommentFilterAdoptionTests -class Darling.Tests.DocCommentHygieneTests \
  -class Darling.Tests.EntraProviderPackageCensusTests -class Darling.Tests.DailyDeadlockWindowCensusTests \
  -class Darling.Tests.MeasurementContractCensusTests -class Darling.Tests.SameStatementPileupSourceCensusTests \
  -class Darling.Tests.FileGrowthRiseUnitCensusTests -class Darling.Tests.PgSettingScrubCandidateCensusTests \
  -class Darling.Tests.McpPayloadContractCensusTests -class Darling.Tests.RemoteCollectorServiceCancellationCensusTests \
  -class Darling.Tests.StoreSessionTimeZonePinCensusTests -class Darling.Tests.StoreApplicationNameCensusTests \
  -class Darling.Tests.MigrationDataMovingRungCensusPins -class Darling.Tests.PlanForceActionDetailCensusTests \
  -class Darling.Tests.WebExceptionTextCensusTests -class Darling.Tests.McpServiceParameterDiSeatCensusTests \
  -class Darling.Tests.ShowPlanParserCondAndMultiplePlanTests -class Darling.Tests.ActualPlanRequestTests \
  -class Darling.Tests.ActualPlanDispatchTests -class Darling.Tests.ActualPlanResultParseTests \
  -class Darling.Tests.QueryModificationDetectorTests -class Darling.Tests.ActualPlanCaptureLoopTests \
  -class Darling.Tests.ActualPlanGatingTests -class Darling.Tests.ReproScriptBuilderHardeningTests \
  -class Darling.Tests.DarlingAnalysisPipelineTests -class Darling.Tests.DarlingMcpPlanToolsSurfaceAndSqlTests \
  -class Darling.Tests.DarlingMcpPlanToolsLivePostgresTests -class Darling.Tests.McpPlanAnalysisEnvelopeTests \
  -class Darling.Tests.SerialLoopStoreSizeSourceTests -class Darling.Tests.TsqlConventionGuardTests

Result: Darling.Tests Total: 530, Errors: 0, Failed: 0, Skipped: 3.

All four builds (Darling.Tests, PerformanceMonitor.Ui, Lite, the Darling Viewer) are Release, -p:EnableWindowsTargeting=true, 0 warnings on every log.

Not run (WPF-dependent, platform reasons): all Viewer* classes that reference PresentationFramework types fail to run on macOS for that reason alone; CI decides them.

Screenshot plan (both hosts, since the control is shared): open a large multi-branch plan with some misestimated operators. Click "Minimap" — the panel appears with the same overview as part 1. Drag the resize grip in the panel's top-left corner and confirm it grows/shrinks between roughly 160px and 500px, re-rendering live; close and reopen the minimap (or load a different plan) and confirm the panel keeps the size you last set. Double-click a minimap node and confirm the main canvas zooms in on it, centers it, and selects it (its properties panel updates). Confirm minimap edges below a misestimated operator pick up the same orange/red (underestimated) or blue (overestimated) tint the main canvas shows for that same edge, instead of the plain neutral colour.

CHANGELOG

SECTION: Changed
ENTRY: - Plan viewer minimap: resize, double-click zoom, and accuracy-coloured edges ([#4603]) - The plan viewer's minimap panel can now be resized and remembers its size across plans, double-clicking a minimap node zooms to and selects it, and minimap edges pick up the same over/underestimate colouring as the main canvas.
REF: [#4603]: #4603