fix: extract text from ContentPart list for UserPromptSubmit hook prompt

[Sibuxiangx]

Problem

The UserPromptSubmit hook event always sends an empty string for the prompt field when the user input comes from the shell UI.

Root cause: In kimisoul.py, user_input passed to run() is typed as str | list[ContentPart]. The shell UI always passes list[ContentPart], but the hook code only extracted text for the str case:

text_input_for_hook = user_input if isinstance(user_input, str) else ""

Fix

Use Message.extract_text() to properly extract text from list[ContentPart], consistent with how text_input is extracted just a few lines later in the same method:

if isinstance(user_input, str):
    text_input_for_hook = user_input
else:
    text_input_for_hook = Message(role="user", content=user_input).extract_text(" ").strip()

Testing

• All 34 existing hook tests pass
• Manually verified: hook now receives {"prompt": "hello this is a test prompt for hook"} instead of {"prompt": ""}

Fixes #1779

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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 1 additional finding.

[Copilot]

Pull request overview

Fixes the UserPromptSubmit hook payload so the prompt field contains the actual user-entered text when the shell UI submits input as list[ContentPart] (instead of always sending an empty string).

Changes:

• Extract text_input_for_hook from list[ContentPart] via Message.extract_text(" ").strip().
• Keep str inputs unchanged while correctly populating the hook’s matcher_value and prompt payload for shell-originated inputs.

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