Add drawing tools proof of concept

[brandtnewlabs]

Summary

• add an internal demo-only trend-line drawing proof of concept
• store drawing anchors in time/price domain coordinates so geometry follows the live chart scale
• render and edit segments through a Skia overlay with UI-thread gesture handling
• provide Browse, Draw, Edit, selection, endpoint dragging, body translation, clear, and short-drag rejection
• add focused tests for clamping, segment distance, hit-testing priority, and immutable translation

Why

A few power users have asked for technical-analysis drawing tools. This spike validates the smallest useful interaction and rendering architecture without committing the library to a broad public drawing API.

User and developer impact

The example app gains a Drawing tools POC under Annotations & overlays. The publishable library API is unchanged.

The POC is intentionally limited to finite trend-line segments. Snapping, rays, undo/redo, persistence, and a public API remain out of scope.

Validation

• npm run verify
  • TypeScript passed
  • ESLint passed
  • 106 test suites passed
  • 1,586 tests passed; 5 skipped
• React Doctor: 100/100, no issues
• iOS simulator QA with agent-device:
  • create a line
  • reject a short drag
  • move either endpoint
  • translate the line body
  • clear drawings
  • hand interaction back to chart scrubbing in Browse mode
  • clean full Metro reload