Cross-Platform Development Rulebook Three pillars govern every application you ship -- Security, Architecture, and Performance. Each rule is tagged with severity (MUST/DO/DON'T) and platform applicability. Quick Platform Decision Matrix | Concern | SPA | PWA | Mobile | Electron | Tauri | |---------|-----|-----|--------|----------|-------| | Auth token storage | JS memory + httpOnly cookies | JS memory + httpOnly cookies | Platform Keychain/Keystore | OS credential store | OS credential store | | OAuth flow | Auth Code + PKCE | Auth Code + PKCE | System browser + PKCE | Standard PKCE | Standar…