Skill-Hub v0.4.0

Ship cross-platform desktop release path

Windows and Linux packaging need more than Tauri's default bundle target: runtime paths differ by OS, updater assets need a merged manifest, and shell-based build scripts do not run on Windows. This change adds platform-aware skill/plugin root discovery, cross-platform frontend path handling, a Node-based Tauri build wrapper, and a GitHub Actions release workflow for macOS, Windows, and Linux artifacts.

Constraint: Codex and Claude roots vary by host OS and can be overridden by CODEX_HOME or CLAUDE_HOME

Constraint: Existing GitHub updater endpoint expects a single latest.json from releases/latest/download

Rejected: Hardcode ~/.codex and ~/.claude everywhere | breaks Windows and alternate app-data installs

Rejected: Build all platforms on the local macOS machine | Tauri desktop bundles require native OS runners

Confidence: medium

Scope-risk: moderate

Directive: Keep updater artifact naming and latest.json platform keys in sync with Tauri bundle output before changing release.yml

Tested: npm run typecheck

Tested: npm run test

Tested: npm run format:check

Tested: cd app/src-tauri && cargo test

Tested: npm run build:desktop

Tested: npm run release:latest-json