Add task publishing helper scripts

[TamaruNorio]

Summary

• Added new_task.ps1 to start a new work branch from the latest main.
• Added publish_pr.ps1 to run preflight checks, commit, push, generate pr_body.md, and show the PR creation URL.
• Added sync_after_merge.ps1 to update main, delete the local merged branch, and run dev_check.
• Added pr_body.md to .gitignore.
• Documented the helper scripts in README.

Test

• .\scripts\dev_check.ps1
• pytest completed
• blocked text scan completed
• logs/real_device/ ignore check completed

Safety

• No real device communication
• real_device_check.py not executed
• logs/real_device/ is excluded from Git
• git push executed manually
• PR creation and merge are manual

Notes

• publish_pr.ps1 requires YES before running git add, git commit, and git push.
• PR creation and merge are not automated.