fix(claude): keep spinner + tokens visible in long TodoWrite blocks

[kbwo]

Summary

• Remove the BUSY_LOOKBACK_LINES = 5 slice in getRecentContentAbovePromptBox. When Claude Code's TodoWrite renders a long checklist inside the same recent block as the spinner header, the cap dropped the spinner + token stats lines and the detector fell through to idle.
• The empty-line boundary introduced in fix: avoid stale Claude busy detection #249 already separates stale redraw fragments, so the additional cap was redundant and only caused false idle detections on long updates.

Repro (before fix)

Claude Code was rendering the following block above the prompt and ccmanager kept the session in idle instead of busy:

✽ Add GitHub Actions workflow and commit… (50s · ↓ 794 tokens)
  ⎿  ✔ Create docs/index.config.json
     ✔ Reorganize existing docs into topic directories
     ✔ Add frontmatter to existing docs
     ✔ Create docs/INDEX.md, docs/README.md, templates, workflow
     ✔ Create root AGENTS.md and README.md
     ✔ Write manifest generation Go script
     ✔ Add Makefile tasks and run first generation
     ◼ Add GitHub Actions workflow and commit

The spinner + tokens line on row 1 was pushed out of the 5-line window by 8 checklist items; none of the remaining 5 lines contained a recognizable busy indicator.

Test plan

• npm run test -- src/services/stateDetector/claude.test.ts (68 passed, including the two stale-guard tests from fix: avoid stale Claude busy detection #249 and the new TodoWrite regression test)
• npm run lint
• npm run typecheck
• Full npm run test