Add persistent directory overrides, Windows engine locality, and Games/Doom defaults

[lock14]

Description

This pull request introduces persistent directory overrides, resolves Windows engine configuration locality and companion asset extraction, standardizes Windows defaults to %USERPROFILE%\Games\Doom\, and performs a code refactoring pass for path and configuration handling:

1. Windows Engine Configuration Locality & Working Directory:

   • On Windows, portable source ports (DSDA-Doom, UZDoom) resolve configurations relative to their program directory ($PROGDIR / BinDir), not %LOCALAPPDATA%. Deploys dsda-doom.cfg and autoexec.cfg directly to BinDir.
   • Sets cmd.Dir = filepath.Dir(plan.EngineBin) in engine/runner.go so executed portable engines read local assets and configurations correctly.

2. Zip Slip Hardened Extraction & Companion File Discovery:

   • Fixed extractZipBinary in engine/installer.go where uzdoom.sf2 matched uzdoom.exe due to prefix matching.
   • Added exact binary matching and companion file extraction (.wad, .pk3, .dll, .sf2, .wopl, .wopn) preserving directory structure.

3. Persistent Asset Directory Hierarchy:

   • Added persistent configuration (config.json) and CLI flags for --wads-dir, --bin-dir, and --soundfonts-dir.
   • Updated doom config get, set, and show to manage all three asset locations with support for short and long environment variable fallbacks (DOOM_* and short forms).

4. Standardized Windows Default Layout:

   • Removed dynamic drive switching heuristic in favor of a deterministic, visible, OneDrive-immune layout:

     %USERPROFILE%\Games\Doom\
     ├── bin\           <-- uzdoom.exe, dsda-doom.exe, autoexec.cfg, dsda-doom.cfg
     ├── wads\          <-- IWADs, PWADs, and DeHackEd patches
     └── soundfonts\    <-- GeneralUser-GS.sf2
     

5. Refactoring & Hygiene:

   • Encapsulated path mutations with paths.SetBinDir() and paths.SetSoundFontsDir() in internal/config.
   • Canonicalized configuration key parsing with canonicalConfigKey() in cmd/doom/config.go.
   • Streamlined flag extraction in cmd/doom/play.go using strings.Cut(arg, "=") against known flag maps.
   • Cleaned up companion file extension checks in internal/engine/installer.go.

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New preset (new community megawad or engine preset in data/presets.json)
• 🚀 New feature (CLI command, engine integration, or asset discovery enhancement)
• 💥 Breaking change (fix or feature that would alter command line flags or existing config paths)
• 🎨 Engine config optimization (tweaks to dsda-doom.cfg or autoexec.cfg)
• 📝 Documentation update (README.md, CONTRIBUTING.md, AGENTS.md)
• 🔧 Tooling / CI / Build configuration

Repository Design & Architecture Checklist

• Declarative Presets: Presets are modified only in data/presets.json; generated files were compiled via doom presets build.
• Portability & Path Invariants: Zero hardcoded usernames or personal paths committed; __HOME__, __RESOLUTION__, __REFRESH_RATE__, and __SOUNDFONT__ placeholders used where appropriate.
• Destructive Safety: Configuration deployment includes timestamped backups (.bak.<timestamp>).
• Strict Line Length: Code complies with the 120-character maximum line length limit.
• Engine Selection: Engine choices, complevels, and DeHackEd load orders are properly configured.

Verification & Testing

• Ran make format-check (or gofmt -s -w .).
• Ran make tidy-check (go.mod and go.sum verified).
• Ran make lint (go vet and revive pass with zero warnings).
• Ran make check (all unit tests pass with -race and -shuffle=on, preset parity, path invariant audit).
• Documentation (README.md, CONTRIBUTING.md, AGENTS.md) is updated and synchronized.