docs: tighten legacy bridge wording

refactor: rename bridge runtime to cli-discord-bridge

docs: rename bridge docs to cli discord bridge

feat: migrate discord bridge to codex

docs: add /connect, /handoff commands and missing env vars to README

feat: add /connect and /handoff commands for session management

Add CLAUDE_MODEL env var to allow runtime model selection

Harden bridge: fix 14 review issues + add --dangerously-skip-permissions support

Replace Chinese ASCII art with Mermaid diagram

Fix Chinese architecture diagram with CJK-aware alignment

Fix Chinese README architecture diagram alignment

Initial release: single-file Discord <-> Claude Code CLI bridge