Restructure README as a landing page

Add download instructions to README

Fix recursive build loop and bundle identifier

Add screenshots to README

Polish README for open-source launch

Add GitHub issues link to Settings page

Polish README: pain-point-driven About, rename to OpenAI Codex

Switch license from MIT to Apache 2.0

Refine README: macOS only, add About section, update features list

Keep rate limit banner Codex-only, remove Claude Code estimation

Show agent name on hover over icon

Redesign agent icons: solid color squares with distinct symbols

Update OpenClaw icon to match official logo

Add rate limit tracking, replace text badges with agent icons

Add pricing dropdown per agent in Settings