feat: track Claude and Codex usage simultaneously

[leonardocouy]

Summary

• Add Codex usage tracking alongside Claude
• Support both OAuth and CLI modes for Codex authentication
• Show combined usage in tray: CL 25% · CX 10%
• Major refactor: split monolithic modules into focused submodules
• Add ts-rs for automatic Rust→TypeScript type generation with CI drift check

Changes

Features

• Track Claude and Codex usage simultaneously
• Codex OAuth mode reads from ~/.codex/auth.json
• Codex CLI mode spawns codex app-server for RPC (session reuse with 5min idle timeout)
• Tray shows both providers with color-coded usage levels

Architecture

• Extract state/, commands/, refresh/, tray/ modules
• Add ts-rs for Rust→TypeScript type generation
• Add CI check for IPC type drift
• Use IpcErrorCode enum instead of string literals
• Add policy.rs for pause/delay logic with unit tests

Bug Fixes

• Reap CLI session on teardown to prevent zombie processes
• Reduce polling loop duplication

Test plan

• Enable Claude tracking only → shows CL X%
• Enable Codex tracking only → shows CX X%
• Enable both → shows CL X% · CX X%
• Codex OAuth mode with valid ~/.codex/auth.json
• Codex CLI mode with codex binary installed
• Settings window reflects both providers
• Notifications work for both providers (near limit, reset)