pyrite create --body-file Doesn't Merge Nested YAML into Frontmatter

Problem

When using `pyrite create --body-file` with content that starts with a YAML frontmatter block (`---\nkind: ...\n---`), the metadata stays in the body instead of being merged into the entry's actual frontmatter. This means component fields like `kind`, `path`, `owner`, `dependencies` aren't indexed and don't appear in `pyrite sw components`.

Reproduction

```bash cat > /tmp/component.md << 'EOF' --- kind: service path: pyrite/services/foo.py owner: core dependencies: [kb-service] ---

Service description here. EOF

pyrite create -k pyrite -t component --title "Foo Service" --body-file /tmp/component.md

Result: the kind/path/owner/dependencies are in the body, not in frontmatter

Expected Behavior

When `--body-file` content starts with a YAML frontmatter block, merge those fields into the entry's frontmatter metadata. The remaining content after the second `---` becomes the body.

Location

`pyrite/cli/__init__.py` or wherever the `create` command processes `--body-file` input.