refactor: idiomatic TypeScript (de-Java-fication)

[DanteCpp]

Summary

Stylistic follow-up to #31 (stacked on lcf). Replaces Java-shaped idioms in the live code with idiomatic TypeScript. No behavioral change — 721 tests, production build, and byte-stable export fixtures all green.

Stacked on #31. Base is lcf; once #31 merges to main, this can be retargeted to main.

Commits

1. Static-utility classes → module functions — LibUtils, GeometricDistances, StandardLayers were all-static classes with a private constructor() (the Java "utility class" pattern). Converted to plain exported functions/consts; importers switched to import * as X, so call sites (X.foo()) are unchanged.

2. Drop the Interface suffix from type names — renamed 7 types and their files to role-based names, avoiding DOM/existing-symbol collisions:
   GraphicsInterface→Graphics, ExportInterface→Exporter, ColorInterface→Color, TextInterface→TextRenderer (DOM Text clash), ShapeInterface→Shape, PolygonInterface→Polygon, ProcessElementsInterface→ElementProcessor.

3. Tool enum — replaced 15 static readonly int constants on ElementsEdtActions with enum Tool. Values stay 0..14 (auto-increment), so the ordering-based dispatch (tool > Tool.HAND) is unchanged. Updated all 151 references; removed 2 dead drag constants.

4. for…of over characters in escapePdfString — the only index loop that was a pure stylistic Java-ism.

Deliberately left as-is

• .fcd wire-format constants — PrimitiveAdvText TEXT_BOLD/ITALIC/MIRRORED are a serialized bitmask (powers of two OR'd together), not an enum; changing them would alter file output.
• Most index loops — they use the index meaningfully (parallel arrays, strides, neighbor access, or semantic layer numbers), so they are not Java-isms.
• get/set accessor pairs — a mechanical method→field conversion is unsafe (shared accessor names across classes; no TS inline-to-field refactor).

Verification

• npm run verify (tsc strict + 721 tests) ✅
• npm run build ✅
• npm run lint — 0 errors (3 pre-existing warnings) ✅