docs: add IDEAS.md with codebase improvement ideas

[clockblocker]

Summary

• Analyzed codebase for improvement opportunities, ranked by severity (High/Medium/Low)
• Documented 8 concrete ideas with data, next steps, and effort estimates
• Key findings: ~31 genuinely unused files, 22 files with raw throws, disabled strict tsconfig, 5 files >500 lines, 9 files with unsafe casts

Ideas

1. (High) Remove unused files detected by knip (~31 real + fix 170 false positives in knip config)
2. (Medium) Standardize error handling — 22 files still use raw throw
3. (Medium) Enable noUnusedLocals / noUnusedParameters in tsconfig
4. (Medium) Split large monolithic files (note-adapter 993L, main.ts 822L)
5. (Medium) Audit 13 unsafe as unknown casts
6. (Low) Reduce 104 deep relative imports via tsconfig paths
7. (Low) Calibrate 3 tunable parameters with TODO markers
8. (Low) Consolidate utils into helper facades (deferred — low urgency)

Test plan

• No code changes — documentation only, review for accuracy

🤖 Generated with Claude Code