refactor: align sync commands with Git

[Jamie-Cui]

Summary

• replace overwrite-style commands with Git-like status, fetch, pull, push, reset, and pull-abort operations
• make push upload committed HEAD only, support force through the same command, and journal interrupted uploads
• close pending pull and push recovery paths, including remote changes after conflict resolution
• align Magit integration, keymaps, English and Chinese docs, and tests with the new breaking API

Validation

• make test (104 tests passed)
• make compile
• git diff --check

The only compile warning is from the third-party webdriver package using an obsolete Emacs macro.