If `git worktree list` fails, we want the Worktrees model to fall back
to an empty slice so callers iterating over it stay correct. The error
branch was setting it to `[]`, but the line below unconditionally
overwrote it with the nil `worktrees` value from the failed call.

Use an else branch so the empty-slice fallback actually sticks.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

The background fetch path already includes PULL_REQUESTS in its
post-fetch refresh scope, but the manual fetch from the files view
doesn't. As far as I can tell that's an oversight from when
PULL_REQUESTS was added — there's no reason the two paths should
differ. Align them so both refresh PRs after fetching.

This also sets up the next commit to extract a shared helper for
the post-fetch refresh.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

The post-fetch logic was duplicated in `backgroundFetch` and the manual
fetch handler: refresh a fixed set of views, then auto-forward branches
if the fetch succeeded. The two had already drifted on the refresh
scope; folding them into a single helper makes the duplication go
away and prevents it from drifting again.

Pass the fetch error through so we preserve the previous behaviour of
refreshing unconditionally but only auto-forwarding on success.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

When the linked worktree's branch is changed externally — by another
shell, by another tool, or by git running outside lazygit — lazygit's
worktrees model goes stale. The next post-fetch auto-forward then
doesn't realise the branch is now checked out elsewhere, and advances
its ref behind the worktree's back. The worktree's HEAD then resolves
to a commit its index/working tree haven't been updated to, and the
user sees that diff as the inverse of what was fetched — files
appearing as pending changes that they didn't make.

The test sets up a linked worktree initially on a side branch, then
externally checks out master in it before pressing fetch. Two
EXPECTED/ACTUAL pairs capture the symptoms: the branches view shows
master as `✓` rather than `↓1`, and switching to the linked worktree
shows master's would-be incoming file as a pending deletion against
HEAD.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

AutoForwardBranches relies on the worktree model to skip any branch
that's currently checked out in another worktree (so we don't update
its ref behind the worktree's back). The post-fetch refresh wasn't
including the worktrees scope, so any external change to the worktree
list between lazygit's startup and the fetch — a `git worktree add`,
a `git checkout` in a linked worktree, a branch rename — left the
in-memory model stale and the skip check returned false negatives.

Add WORKTREES to the post-fetch refresh scope when auto-forwarding is
enabled. We gate on the config so users with auto-forward disabled
don't pay for an extra `git worktree list` plus per-worktree rev-parse
on every fetch tick.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>