Simulate a merge conflict scenario: (1) Create repo with file.txt, (2) Branch feature-A: modify line 3, (3) Branch feature-B: modify same line 3 differently, (4) Merge feature-A to main, (5) Merge feature-B to main → CONFLICT. Show: conflict markers (<<<<<<<, =======, >>>>>>>), how to resolve manually, git mergetool, git merge --abort. Best practices to avoid conflicts.
