feat(render): clarify selected route line ownership

[adot-7]

Closes #74

Summary

• render selected route geometry in its actual family/line colors
• use restrained spaced markers and deterministic multicolor transfer rings
• dim unrelated network lines only while a route is ready
• add synthetic curved transfer, determinism, bounds, and viewport tests

Checks

• gofmt
• go test ./...
• go vet ./...
• go build ./...
• git diff --check

Visual evidence is covered by focused native terminal renderer tests at normal 100x30-style and 50-column boundary sizes. No live/schedule behavior changed.