Todo widget, iteration cap fix, widget result matching

[mfwolffe]

Summary

• c252d07 — TodoListWidget with [x]/[~]/[ ] checkboxes and strikethrough, rendered above input area
• 4545623 — Raise max_iterations 15 → 200; text loop detector is the real termination mechanism
• 50fe254 — Emit visible error when iteration cap is hit instead of silent exit
• 1c7aa50 — Strengthen TodoWrite prompt guidance for 3+ step tasks
• 96d92d0 — Match tool widgets by name instead of FIFO to prevent result/widget swaps

Test plan

• uv run pytest — 416 pass
• Multi-step task produces TodoWrite calls and visible checklist
• Tool results display under correct widgets (read shows file content, bash shows ls output)
• Turns with 15+ iterations complete without silent truncation