fix: delete steps and elements on message edit

[Allaoua9]

Problem

When a user edits a message, child steps and elements from previous executions were never deleted from the data layer. This caused all historical steps to accumulate and reappear in the UI after each edit.

This is based on this PR .

cc @hayescode this PR addresses your concern on orphaned Elements and Feedbacks.

[Allaoua9]

PR 2856 should be closed in favor of this.

[cubic-dev-ai]

2 issues found across 3 files

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="backend/tests/test_message.py">

<violation number="1" location="backend/tests/test_message.py:897">
P2: This assertion is too loose and can miss extra delete_* calls, so the test may not catch over-deletion regressions.</violation>

<violation number="2" location="backend/tests/test_message.py:897">
P2: Deletion tests check async data-layer calls with call assertions instead of await assertions, so they would miss a missing-`await` regression.</violation>
</file>

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