[keysmon]

Fixes #334.

Shift-line terrain painting currently ignores the selected brush size. This applies the brush at each line anchor using whole-tile offsets, and keeps the original brush settings for redo. Short and zero-length previews use the placement mutation so their footprint matches the brush. Adjusted endpoint handling also allows short multi-cell strokes to commit correctly.

Height-changing placement and previews now refresh cell lighting. Final review caught stale brightness in the short-preview path; nine regression cases reproduced it before the correction.

Validation

• 65 tests passed: 36 editor regression cases and 29 existing MCP cases. Brush and lighting regressions were verified failing before their fixes.
• 2,112 headless cursor/mutation scenarios passed across TS and YR cell settings, covering brush sizes, multi-cell/sparse tiles, eight directions, AutoLAT, boundaries, preview cleanup and undo/redo. These use synthetic map/TMP data through the real handlers.
• @keysmon checked the original and fixed brush behavior through CrossOver on macOS: 3x3/5x5 sand strokes, AutoLAT previews, multi-cell road placement and undo/redo, including redo after changing brush size. Those GUI checks precede the master rebase and lighting follow-up; automated checks were rerun afterward.

Native Windows verification is still outstanding. Local editor/test builds passed with content compilation disabled. The full solution has an inherited missing external Rampastring.Updater dependency that also fails on pristine source. Keeping this as a draft for review and Windows validation.

Screenshots

With a 3x3 brush selected, the original Shift stroke remains one tile wide:

The fixed 3x3 stroke uses the brush width:

A 5x5 brush produces a wider stroke:

Implementation, automated tests and this PR description were prepared with Codex assistance. Manual observations and screenshots are from @keysmon.