Improve todo and reasoning presentation

[zcmx]

Changes

Make todo and reasoning blocks easier to read in chat.

• Render todowrite and todoread as structured task lists instead of raw JSON.
• Show task status, priority, and overall progress.
• Visually distinguish completed and cancelled tasks.
• Show a short contextual title for collapsed reasoning blocks instead of repeating Reasoning.
• Read the title from metadata or the first meaningful reasoning line.
• Remove bold Markdown markers from collapsed titles.
• Keep the expanded reasoning content unchanged so Markdown formatting still works.
• Fall back to the standard tool view when the todo payload format is unknown.

Model persistence, foreground recovery, the apply-patch widget, and the hardened build are not included.

Verification

• TodoToolWidgetTest
• ReasoningTitleTest
• git diff --check