fix(editor): require pointer movement before extending drag selection

[luccas-harbour]

Summary

• Fix SD-2356: clicking into a table (or anywhere in the document) could select text because tiny pointer jitter on mousedown immediately engaged drag selection.
• Gate drag selection and edge auto-scroll behind a 5px Euclidean movement threshold from the drag start point, matching the distance gating already used for multi-click detection.
• Once the threshold is exceeded for a given drag, it stays exceeded until the drag ends (so you can't drop back below the threshold mid-drag).

Changes

• packages/super-editor/src/editors/v1/core/presentation-editor/pointer-events/EditorInputManager.ts
  • New DRAG_SELECTION_DISTANCE_THRESHOLD_PX = 5 constant.
  • Track #dragStartClient and #dragThresholdExceeded state; reset wherever drag state is cleared (drag start, end, cancel, teardown).
  • New #hasExceededDragSelectionThreshold() helper; pointer-move handler returns early before extending selection or updating auto-scroll until the threshold is crossed.
• packages/super-editor/src/editors/v1/core/presentation-editor/tests/EditorInputManager.dragAutoScroll.test.ts
  • Movement of (3, 3) stays below threshold → no dispatch / scheduleSelectionUpdate.
  • Movement of (3, 4) reaches the Euclidean threshold → exactly one selection extension.
  • Edge auto-scroll does not start while pointer movement stays below the threshold near the edge.

[linear]

SD-2356 BUG: Clicking into table in specific document jumps user to other part of document

[codecov-commenter]

Codecov Report

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