docs: add wiki pages for all audiences, fix .old.yml leak

9 new wiki pages: getting-started, faq, troubleshooting,
advanced-usage, verification-modes, adding-a-platform,
adding-a-scraper, testing-guide, release-process.

Updated architecture.md with mermaid diagrams, tools.md with
full pipeline and target/exporter sections, profiling.md with
missing fields, index.md with glossary and nav links.

Expanded CONTRIBUTING.md from stub to full contributor guide.

Filter .old.yml from load_emulator_profiles, generate_db alias
collection, and generate_readme counts. Fix BizHawk sha1 mode
in tools.md, fix RetroPie path, fix export_truth.py typos.

scripts/generate_db.py

@@ -401,6 +401,8 @@ def _collect_all_aliases(files: dict) -> dict:
         try:
             import yaml
             for emu_file in emulators_dir.glob("*.yml"):
+                if emu_file.name.endswith(".old.yml"):
+                    continue
                 try:
                     with open(emu_file) as f:
                         emu_config = yaml.safe_load(f) or {}