A test pins the local terminal's log graph across a merge: two lanes that join, and a narrow pane that keeps the graph #7070

The log (src/tui/local/log.ts) draws its graph from graphLanes in src/git/local.ts. The only test is a straight line of commits.

Done:

• [ ] A new test makes a branch, commits on both sides and merges. The log shows two lanes that join at the merge, in order, with every commit once.
• [ ] At 40 columns the graph column is still drawn and no row overflows the pane.
• [ ] Enter on a commit opens its diff.

Files: test/tui-local-log-graph.test.ts

The test drives createLocalApp (src/tui/local/app.ts) over a real temporary repository, as test/tui-local.test.ts does. If it finds the behaviour wrong, fix the screen in the same pull and say so. If the check fails in a test this pull does not touch, name it in the pull rather than widening the change.

Before pushing: bun x tsc --noEmit and the new test.