[Mehulsri07]

A Section screen: draw a line (it can bend) on the map, and see the ground along it.

• Heights are feet above sea level, so layers line up by height on sloping ground.
• 200 proposed columns along the line, in the same strengths as on the Map: faded (likely), paler (rough guess), hatched (not enough data).
• Borewells within 250 m – 2 km of the line (500 m by default) drawn solid, with their IDs; thinned as in StrataField when there are too many.
• The expected water line where recent readings exist, the ground line, and where the line bends.
• Save as picture (PNG) and Save as PDF (one A4 landscape page with the line's length, the borewell count, the key and the fixed "proposals, not measurements" line). Light colours whatever the app's theme.
• Click a borewell to put the line through it; Undo last point; Clear. A double-click is one point, not a bend.

New libraries (all already used by StrataField): pdf-lib, Tauri's dialog and fs plugins (Save dialog only; the records stay read-only).

Checks: 131 unit tests (section along a bent line, sloping ground, corridor, missing ground height, water, repeated points, PDF page, saved-picture colours and text size); a 500-borewell section takes ~75 ms; the real-app test draws a section on made-up borewells.

Review fixes: the saved picture lost the 11px text size; repeated points made fake bends; borewells just past the ends are drawn at the ends; the right message off the ground-height data; "How good are these estimates?" link on this screen too.