refactor(coding-agent): renamed todo_write tool to todo

- Renamed `TodoWriteTool` to `TodoTool` and its source/prompt files.
- Updated tool registration, schema, renderers, and gating to `todo`.
- Adjusted cursor provider native tool names and tests to match.
- Renamed strike-animation constants and `todo-error-reminder` type.

packages/coding-agent/src/cli/args.ts

@@ -313,7 +313,7 @@ ${chalk.bold("Available Tools (default-enabled unless noted):")}
   inspect_image - Analyze images with a vision model
   browser       - Browser automation (Puppeteer)
   task          - Launch sub-agents for parallel tasks
-  todo_write    - Manage todo/task lists
+  todo          - Manage todo/task lists
   web_search    - Search the web
   ask           - Ask user questions (interactive mode only)