fix(notebook): cascade-delete chat sessions on notebook deletion

[lfnovo]

Problem

DELETE /api/notebooks/{id} removed the notebook, its notes, and (optionally) its exclusive sources, but left chat_session records orphaned in the database.

Change

• Extend Notebook.delete() to enumerate the notebook's chat sessions via the existing get_chat_sessions() method (the refers_to graph relation) and delete each one, matching the ordering and error handling of the existing notes/sources cascade. The returned counts dict gains deleted_chat_sessions.
• Notebook.get_delete_preview() and the NotebookDeletePreview response now report chat_session_count, so the API no longer understates what a delete will remove.

Tests

• Added test_notebook_delete_cascades_chat_sessions — asserts each chat session is deleted and the count is returned.
• Added test_notebook_delete_preview_counts_chat_sessions — asserts the preview reports the chat session count.
• Full suite: 557 passed. ruff check . and mypy clean.

Closes #1124

[cubic-dev-ai]

1 issue found across 5 files

Confidence score: 3/5

• In open_notebook/domain/notebook.py, the delete flow still does not surface that associated chat sessions will also be removed because NotebookDeletePreview/dialog rendering omits the new field, so users can confirm deletion without informed consent and lose conversations unexpectedly. Extend NotebookDeletePreview plus the delete dialog and related i18n copy to explicitly show this warning before merging.

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Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="open_notebook/domain/notebook.py">

<violation number="1" location="open_notebook/domain/notebook.py:210">
P2: Notebook deletion still gives no UI warning that chat sessions will be removed: the dialog's typed preview omits and never renders this new field. Extend `NotebookDeletePreview` and the delete dialog/i18n copy to display `chat_session_count`, so users can see this additional destructive effect before confirming.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Notebook deletion still gives no UI warning that chat sessions will be removed: the dialog's typed preview omits and never renders this new field. Extend NotebookDeletePreview and the delete dialog/i18n copy to display chat_session_count, so users can see this additional destructive effect before confirming.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At open_notebook/domain/notebook.py, line 210:

<comment>Notebook deletion still gives no UI warning that chat sessions will be removed: the dialog's typed preview omits and never renders this new field. Extend `NotebookDeletePreview` and the delete dialog/i18n copy to display `chat_session_count`, so users can see this additional destructive effect before confirming.</comment>

<file context>
@@ -202,6 +207,7 @@ async def get_delete_preview(self) -> Dict[str, Any]:
                 "note_count": note_count,
                 "exclusive_source_count": exclusive_count,
                 "shared_source_count": shared_count,
+                "chat_session_count": chat_session_count,
             }
         except Exception as e:
</file context>