docs: fix Notification hook matcher example

[he-yufeng]

Summary

• replace the non-functional permission_prompt Notification hook example with real background-task notification types
• correct the Notification matcher wording in the English and Chinese hook docs
• update the hook config roundtrip fixture so it no longer preserves the broken matcher

Fixes #2330

To verify

• uv run --package kimi-cli --group dev pytest tests/hooks/test_integration.py::test_config_roundtrip_toml tests/hooks/test_integration.py::test_notification_hook -q -p no:cacheprovider
• uv run --package kimi-cli --group dev ruff check tests/hooks/test_integration.py
• git diff --check

Note: running the whole tests/hooks/test_integration.py file on Windows still hits existing shell assumptions around bash/python3; the two tests touched by this patch pass.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.