fix: cancel edited commit message on interrupt

[pupuking723]

Fixes #560.

This prevents the Edit commit-message prompt from treating Ctrl+C as a literal commit message.

Root cause:

• @clack/prompts returns a cancel symbol when the text prompt is interrupted.
• The Edit path converted that value with toString(), so Symbol(clack:cancel) could be passed to git commit -m.

Changes:

• Check isCancel(textResponse) before using the edited commit message.
• Add an e2e regression test that interrupts the Edit text prompt and verifies no commit is created.
• Keep the normal Edit flow covered to make sure edited commit messages still commit correctly.

Verification:

• npm run build
• npx jest test/e2e/cliBehavior.test.ts -t "cli flow cancels when editing the generated commit message is interrupted"
• npx jest test/e2e/cliBehavior.test.ts -t "cli flow allows editing the generated commit message before committing"
• npm run lint