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

[SomethingNew71]

Summary

Ports upstream PR #367 — implements the `pdf` output format that's been a TODO stub since v0.4.1. Pipes the graph through Graphviz's PDF renderer and dispatches the bytes the same way PNG goes: file in normal mode, `sys.stdout.buffer` in stdout mode.

Usage

```bash
wireviz -f P harness.yml # produces harness.pdf
cat harness.yml | wireviz -f P -O - - # binary PDF to stdout
```

Changes

• `format_codes`: un-commented `"P": "pdf"` (use `-f P` on the CLI)
• `Harness._render()`: new `pdf` branch using `graph.pipe(format="pdf")`
• `Harness.output()`: removed the "PDF output is not yet supported" stderr warning

Differences from upstream PR wireviz#367

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 #2 in this fork), so PDF works in both file AND stdout modes without extra plumbing. Also doesn't commit the example PDF artifacts — those are graphviz-version-dependent like SVG/PNG, and the project's "owner will rebuild" convention applies.

Verification

• ✅ `wireviz -f P harness.yml` produces a valid PDF (file v1.7)
• ✅ `cat harness.yml | wireviz -f P -O - -` writes valid PDF to stdout
• ✅ `build_examples.py` deterministic outputs byte-identical

🤖 Generated with Claude Code

[SomethingNew71]

@tobiasfalk — heads up, your upstream #367 (Complete PDF output handler) is being incorporated here.

Context: We use WireViz to document Classic Mini Cooper wiring harnesses at Classic Mini DIY and are building a GUI on top of it. This is your second PR we've pulled in (after #379 output_dpi) — appreciate the work.

The port uses the in-memory graph.pipe(format="pdf") path from PR #2 in this fork (the stdin/stdout streaming port of upstream wireviz#321) instead of the graph.render() + temp-file path your original PR used. Side benefit: PDF works for wireviz -f P -O - - (binary PDF to stdout) without any extra plumbing.

Commit attribution links back to your PR. Thanks!

[gemini-code-assist]

Code Review

This pull request implements PDF output support by enabling the 'P' flag in the CLI and adding the rendering logic in the Harness class. A review comment notes that the current implementation only renders the Graphviz diagram, which contradicts documentation stating that PDF output should also include the Bill of Materials (BOM); it is suggested to either update the documentation or extend the PDF generation to include the BOM.

[gemini-code-assist]

The current implementation of PDF output only renders the Graphviz diagram. However, the docstring in src/wireviz/wireviz.py (line 55) states that the PDF format includes "the diagram and (depending on the template) the BOM".

Since this implementation only pipes the graph to PDF, the resulting file will miss the summary Bill of Materials (BOM) table that is present in the HTML output. To maintain consistency with the documentation, you should either update the docstring in wireviz.py to clarify that PDF only contains the diagram (consistent with PNG and SVG), or consider extending the implementation to include the BOM.