Mirrors dashboard `resolveDiffBase` display-recovery: when `baseBranch` is
absent, compute `merge-base(HEAD, main)` and prefer it over a stale
`baseCommitSha` only if it strictly descends that SHA. Pre-merge rebase
on legacy/imported tasks (no recorded baseBranch) was producing inflated
"N files changed outside declared File Scope" warnings — FN-3898 surfaced
17 ghost files for a 3-file change.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
985d51c3b3