fix: reject overlapping portal lines during creation

[ai-eks]

Summary

• reject a portal pair when both lines overlap or share an endpoint on the same display edge
• keep the editor on the second-line step and show a localized red validation message
• add coverage for overlap, endpoint touching, separated lines, and final build validation
• bump the app version to 1.0.1 (build 2)

Why

A portal could previously be created with both endpoints occupying the same edge range. In edge cases this can cause ambiguous bidirectional cursor warping. Validation now happens while creating the second line and again before building the portal.

User impact

Invalid second lines are not saved. The editor explains the problem and lets the user redraw the second line immediately.

Validation

• swift test — 112 tests passed
• git diff --check