Merge main into 4111 table border branch

Goal

Merge main into codex/4111-table-border-wrong-cell, resolve conflicts cleanly, and verify the branch is in a good state.

Scope

• switch to codex/4111-table-border-wrong-cell
• merge main
• resolve merge conflicts without dropping intended branch work
• run narrow verification based on touched files

Progress

• 2026-03-31: Started merge task and captured plan.