prepare_reference_data: handle dict entries with missing or non-string id

[simpleqt]

Fixes #2448

Summary

prepare_reference_data in src/memos/mem_os/utils/reference_utils.py handles TextualMemoryItem objects and raw dicts, but the dict branch assumes every key exists and that id is a string:

>>> prepare_reference_data([{"metadata": {"memory": "m"}}])
KeyError: 'id'
>>> prepare_reference_data([{"id": 12345, "memory": "m", "metadata": {}}])
AttributeError: 'int' object has no attribute 'split'

Both escape the streaming pipeline for memory entries that are not TextualMemoryItem instances (e.g. already-serialized dicts from a cache or an MCP payload).

Fix

Read the id defensively: derive ref_id from the string form when an id exists, skip it otherwise. TextualMemoryItem behavior is unchanged.

Regression test

Added tests/mem_os/test_prepare_reference_data.py:

• red/green verified: the two crash cases fail against the old implementation and pass with the fix
• pins the TextualMemoryItem and string-id dict paths as unchanged

ruff check (repo-pinned 0.11.8) passes on both touched files.

AI Disclosure

• Tool(s): Claude (ZCode CLI)
• Used for: debugging assistance, code suggestions, and drafting this PR description. All changes human-reviewed.

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[Memtensor-AI]

🤖 Open Code Review

Target: PR #2449
Task: 350cec654abe26f4
Base: main
Head: sq/reference-data-dicts

✅ OpenCodeReview: Review complete: 0 finding(s) across 2 selected item(s).

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[Memtensor-AI]

✅ Automated Test Results: PASSED

All tests passed (4/4 executed). memos_python_core/changed-repo-python: 4/4. Duration: 8s [advisory, non-gating] AI-generated tests on branch test/auto-gen-350cec654abe26f4-20261001000641: 44/44 passed — these do NOT affect the PR verdict; review the branch manually.

Branch: sq/reference-data-dicts