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.

[Randy-sin]

One remaining doc mismatch: this patch fixes the example and matcher table, but the use-case list above still says desktop notifications can "Send alerts when human approval is needed" / "在需要人工审批时发送通知".

Since approval requests are not Notification events, that sentence would still leave the page claiming approval notifications are supported after this change. I would change it to background task notifications, or add an explicit note that approval requests currently are not emitted through the Notification hook.

[he-yufeng]

Follow-up pushed in 5aec6ff.

Updated the top use-case list in both English and Chinese docs to use background task notifications instead of human approval notifications.

Validation on Windows:

• git diff --check
• uv run pytest tests/hooks/test_integration.py::test_config_roundtrip_toml -q: 1 passed
• uv run ruff check tests/hooks/test_integration.py
• uv run ruff format --check tests/hooks/test_integration.py

Note: the full tests/hooks/test_integration.py file still has existing Windows shell/python3 failures unrelated to this doc-only change.