Preview markdown, and say what a file with no diff is

[siegfriedpammer]

Two small reading features, one commit each.

Markdown preview (m, or View > Markdown Preview)

A change to a README or a document is read for what it will look like as much
as for what it says, and the diff can only show the source. The preview opens
as a tab of its own, so the source and the rendering are open at once:

• renders the head side — what the change produces — and the base side for
  a file the change deletes, which has no head side left;
• reuses the renderer, link command, selection handling and emphasis repair
  that the overview's description already uses, so it picks up whatever those
  learn. No new dependency, no new markdown code;
• enabled only where there is something to render. On a .cs file the menu
  item is greyed rather than silently doing nothing;
• typing m into a comment still types an m — the gesture handlers already
  stand aside for a text box.

Files with no diff are pointed out

A binary file, and a file that changed without its content changing (a rename,
a permission bit), were both built as a diff of two empty sides. That opens as
a blank document, which a reader cannot tell from a tool that failed to
load the file — and the changed-files list showed them with no counts at all,
beside files that genuinely changed nothing.

Now the tab says which of the two it is, and for a binary file how the sides
compare in size — whether the image got bigger is the whole of what a review
can say about it, and git knows it via cat-file -s without reading the blob:

logo.png

Binary file: git compares the bytes and reports only that they differ, so there
is no textual diff to read.

Modified.  12 KB -> 14 KB (+2 KB)

The file list carries the same word (binary / no lines) where the counts
would be. It is still the file's own tab with the file's own path, so it can
be marked viewed and stepped past like any other — a binary file is part of a
change, and a reader ticking files off should not have to skip it.

Testing

Build clean, 0 warnings. 353 tests, 352 passing, 1 skipped (the pre-existing
basedpyright bootstrap); 11 new cases cover the description and size logic,
which is a pure function in Stampeded.Core.

Both features were driven in the running app against a scratch repo holding a
markdown change, a pure rename and a binary change — the preview via both the
menu and the m key, the binary page and the list badges by opening them.

Deliberately not included

The overview's cost table still shows +0 -0 ~0 min for these files. That
reads as accurate there — nothing to read is zero minutes — and a column for
it would be the one place this got wider rather than clearer. The queue you
pick files from and the document you open both say it, which is where the
question is asked.

🤖 Generated with Claude Code