Align parse() PDF docstring with diagram-only reality (PR #8 review feedback)

Addresses gemini-code-assist feedback on
#8 — the prior docstring
claimed PDF includes "the diagram and (depending on the template) the
BOM", which was carried over from upstream's never-completed PDF stub
plan.

The actual implementation in this PR pipes the graph through
Graphviz's PDF renderer (graph.pipe(format="pdf")), which produces a
diagram-only PDF with no embedded BOM table. That matches the PNG/SVG
behavior and is the right scope for a fork that already exposes
HTML+SVG embed for richer output.

Embedding the BOM in PDF would require a full document-composition
step (PIL or reportlab) that's well outside the scope of "implement
the missing format flag" — and HTML output exists for users who want
diagram + BOM in one artifact.

No code change; docstring only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: SomethingNew71

src/wireviz/wireviz.py

@@ -53,7 +53,7 @@ def parse(
         * "gv":   the diagram, as a GraphViz source file
         * "html": the diagram and (depending on the template) the BOM, as a HTML file
         * "png":  the diagram, as a PNG raster image
-        * "pdf":  the diagram and (depending on the template) the BOM, as a PDF file
+        * "pdf":  the diagram, as a PDF document (no BOM — see "html" for that)
         * "svg":  the diagram, as a SVG vector image
         * "tsv":  the BOM, as a tab-separated text file