fix(commit): collapse and cap the auto-staging untracked listing

[max-sixty]

#4111 switched the status read behind the auto-staging warning to -uall, so the warning sees untracked files that status.showUntrackedFiles=no hides. That flag also expands every untracked directory into its files, so wt step commit, wt step squash, and wt merge listed 300 paths for a directory of 300 new files before committing.

The warning now reads git's normal untracked mode instead. It still overrides status.showUntrackedFiles=no, but names a wholly untracked directory once as dir/, so a directory of generated files takes one row and can't push a separate new file out of view. The file count stays visible in the commit progress line that follows.

The listing also stops at ten rows. Past ten paths it lists nine and a hint counts the rest, so the hint always stands for at least two paths:

▲ Auto-staging 11 untracked paths:
   ┃ 0-generated/
   ┃ 01.txt
   ┃ …
   ┃ 08.txt
↳ … and 2 other paths
◎ Generating commit message and committing changes... (310 files)

The status read also moves into the warning itself. Commit and squash each built that command before calling the warning, one through WorkingTree and one through Repository; both now go through the WorkingTree they stage.

Thanks to @Duang777, whose #4112 proposed the cap. They're credited as co-author.

This was written by Claude Code on behalf of max-sixty

🤖 Generated with Claude Code

[worktrunk-bot]

The cap itself is right, and the nine-plus-hint arithmetic checks out (over the cap the hint always stands for at least two paths, so the plural is never wrong). One consequence of where the cut lands is worth a decision.

git status -uall emits paths in sorted order, so a single untracked directory with ten or more files fills every row on its own and the rest of the worktree is never named:

$ git status --porcelain -uall
?? apples/1.txt
?? apples/10.txt
... (apples/11, 12, 2..9)
?? secrets/key.pem

That renders as nine apples/* rows and … and 4 other paths. secrets/key.pem is about to be staged by git add -A and the user is not told. Before #4111 the same worktree listed two rows — apples/ and secrets/ — because git's default untracked mode collapses directories; #4111 switched the read to -uall for the count, and the cap now spends the whole listing on whichever directory sorts first. The count line covers the "300 paths, something is wrong" case on its own, but in the moderate case (say 15 paths across three directories) it is the which areas detail that makes the warning actionable, and that is the part the cap drops.

A shape that keeps both: count with -uall as now, and build the capped listing from the collapsed entries, so every untracked directory gets a row and the cap only bites past nine distinct areas.

Raising this for a decision rather than blocking — it is a judgment call about what the warning is for, and capping is an improvement over printing 300 rows either way.