feat(repo): auto-name worktrees from topic slug

[DeepColds]

Summary

• generate semantic worktree slugs from the topic title, falling back to the first pending prompt
• optionally use an OpenAI-compatible AI slugger to translate/summarize Chinese or mixed-language task text into concise English slugs
• keep deterministic local slug/hash fallback when AI is disabled, misconfigured, slow, or returns invalid output
• use the slug for both auto branch names (wt/<slug>) and sibling worktree dirs (<repo>-wt-<slug>), with -2 style collision handling
• keep explicit branch arguments unchanged and update help/usage copy

Config

AI slugging is disabled by default. Enable with:

• BOTMUX_WORKTREE_SLUG_AI_ENABLED=true
• BOTMUX_WORKTREE_SLUG_AI_BASE_URL=<openai-compatible-base-url>
• BOTMUX_WORKTREE_SLUG_AI_API_KEY=<api-key>
• BOTMUX_WORKTREE_SLUG_AI_MODEL=<model>

Optional:

• BOTMUX_WORKTREE_SLUG_AI_TIMEOUT_MS (default 5000)
• BOTMUX_WORKTREE_SLUG_AI_EXTRA_HEADERS
• BOTMUX_WORKTREE_SLUG_AI_EXTRA_BODY

Tests

• pnpm vitest run --project unit test/git-worktree.test.ts test/worktree-slug-ai.test.ts test/command-handler.test.ts test/card-handler-repo-select.test.ts
• pnpm tsc --noEmit