Wire up PDF output (port of upstream PR wireviz#367)

Implements the ``pdf`` output format that's been a TODO stub since
v0.4.1. Pipes the graph through Graphviz's PDF renderer
(``graph.pipe(format="pdf")``) and dispatches the bytes the same way
PNG goes — to a file in normal mode, to ``sys.stdout.buffer`` in
stdout mode.

Usage:

    wireviz -f P harness.yml                 # produces harness.pdf
    cat harness.yml | wireviz -f P -O - -    # stdout, binary

CLI flag changes:
* ``"P": "pdf"`` un-commented in ``format_codes`` (use ``-f P``)
* "PDF output is not yet supported" stderr warning removed from
  Harness.output()

Adapted from wireviz#367 (originally
by @tobiasfalk, targeting upstream ``dev``). The upstream patch went
through the old ``graph.render()`` + temp-file path — this port uses
the in-memory ``graph.pipe()`` wired up by the stdin/stdout refactor
(PR wireviz#321), so PDF works in both file mode AND stdout mode without
extra plumbing.

Verified:
* ``wireviz -f P harness.yml`` produces a valid PDF (file 1.7).
* ``cat harness.yml | wireviz -f P -O - -`` writes valid PDF to stdout.
* build_examples.py: deterministic outputs (.gv, .bom.tsv) byte-
  identical (no example .yml has been switched to request PDF
  rendering — keeping that out of the regression baseline since PDF
  bytes from graphviz vary by version).

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

Author: SomethingNew71

src/wireviz/Harness.py

@@ -698,9 +698,6 @@ def output(
         if "csv" in fmt:
             # TODO: implement CSV output (preferably using CSV library)
             sys.stderr.write("CSV output is not yet supported\n")
-        if "pdf" in fmt:
-            # TODO: implement PDF output
-            sys.stderr.write("PDF output is not yet supported\n")
 
         if filename is None:
             # stdout mode — emit each rendered format in the user-requested order
@@ -763,6 +760,9 @@ def _render(
             png_bytes = graph.pipe(format="png")
             outputs["png"] = png_bytes
 
+        if "pdf" in fmt:
+            outputs["pdf"] = graph.pipe(format="pdf")
+
         if "gv" in fmt:
             outputs["gv"] = graph.source
 

src/wireviz/wv_cli.py

@@ -18,7 +18,7 @@
     "g": "gv",
     "h": "html",
     "p": "png",
-    # "P": "pdf",
+    "P": "pdf",
     "s": "svg",
     "t": "tsv",
 }