Brace expansion patterns like `{doc1,doc2}.md` or `collection/{a,b}.md`
were incorrectly parsed as comma-separated file lists instead of being
passed to the glob matcher (picomatch). This happened because the
comma-detection heuristic only checked for `*` and `?` but not `{`.
Also adds `collection/path` matching in `matchFilesByGlob` so patterns
like `my-collection/{file1,file2}.md` work — previously the glob only
matched against `qmd://collection/path` (virtual) and `path` (relative
to collection root), missing the `collection/path` form.
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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