fix(picker): a non-git Project shows no marker and a muted not a git repo (#87)

[hammadmajid]

What changed

A directory added with cdd add that is not a git repo no longer reads as a failure. git.GetStatus already reports NotRepo (no .git) separately from Unknown, so only the Picker's rendering changed:

• the row shows no marker for NotRepo (its status column width is 0)
• the preview shows a muted not a git repo; branch and sync stay omitted
• the red ! stays for Unknown (a real git failure in a repo). Its preview text is now git could not read it, since Unknown is not only a timeout
• the legend is unchanged: ! still means unknown, and a non-git row shows no glyph to explain

How verified

• new view tests: non-git row and preview (TestView_NotRepoIsNeutral), and Unknown keeping its ! (TestView_UnknownStaysRed); the existing status-keying test now uses Unknown for its ! row
• gofmt -l . empty, go vet ./... and golangci-lint run ./... clean
• go test ./... passes except the known local-only fish cases of TestScriptExecution

Closes #87