[codex] Fix section footer border rendering

[mcclayton]

Summary

• Move the section footer out of the rounded bottom border and into a right-aligned interior row.
• Keep the bottom border continuous so narrow section boxes do not look broken.
• Normalize framework-owned Unicode glyphs before measuring visible line width so selected rows with the ▶ pointer align even when the shell locale is not UTF-8.
• Update UI line counting for footer rows and add a regression test for the ASDF section menu.

Validation

• bash ./ci/test_ui.sh
• bash ./ci/checks.sh
• git diff --check