feat(infra): add Windows platform support and safe asset loading

[kassyi]

Summary

• Add windows-shell := "pwsh.exe" to workspaces justfile configs
• Implement get_main_script_path() and get_main_style_path() in assets.rs to safely resolve WebView assets on Windows
• Add conditionally compiled #[cfg(unix)] directives to ipc/socket.rs to fix dead_code and unused import warnings failing the CI

Previously, Windows builds would fail during the just check phase because sh is unavailable natively on Windows, and because asset:// protocols behaved differently than local absolute paths (C:\). This PR establishes the baseline necessary for Windows compatibility and ensures the CI pipeline passes on Windows environments.

2026-04-05.033210.mp4

Test plan

• Verify just check executes cleanly via PowerShell (pwsh) on Windows
• Verify the app compiles and launches natively on Windows without failed to load asset errors for main.js and main.css
• Verify CI pipeline completes the Windows target build matrix successfully

Related issues

• feat: add Windows support #158

[lambdalisue]

I don't understand why this PR includes style: run formatter (oxfmt) in reader or similar commits and that prevent me to review the PR. Please focus a single purpose.

If styles things are broken in main branch, please first explain the reason and create an isolated PR for fixing that.