fix: add missing text_lemmatized in AsyncMemory._create_memory

[ixchio]

Linked Issue

This is a newly discovered bug — no existing issue.

Description

AsyncMemory._create_memory was missing the text_lemmatized field computation, unlike its sync counterpart Memory._create_memory (line 1591). This caused all memories created via AsyncMemory with infer=False to be invisible to BM25 keyword search, silently degrading search recall for all async users.

Root Cause

When _create_memory was ported from sync to async, the lemmatize_for_bm25() call was accidentally omitted. The sync version stores:

new_metadata["text_lemmatized"] = lemmatize_for_bm25(data)

But the async version at line 2994 was missing this line entirely. The hybrid scoring pipeline (semantic + BM25 + entity boost) relies on text_lemmatized for keyword matching — without it, BM25 scores are always zero for affected memories.

Impact

• All AsyncMemory users using infer=False are silently affected
• Keyword search recall drops to zero for memories created via the async path
• No error is raised — the bug is completely silent, making it hard to detect

Fix

One-line addition to AsyncMemory._create_memory to compute and store text_lemmatized, matching the sync implementation.

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Refactor (no functional changes)
• Documentation update

Breaking Changes

N/A

Test Coverage

• I added/updated unit tests
• I added/updated integration tests
• I tested manually (describe below)
• No tests needed (explain why)

Added two regression tests:

• test_sync_create_memory_stores_text_lemmatized — parity check confirming sync version works
• test_async_create_memory_stores_text_lemmatized — regression test that would fail without this fix

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have added tests that prove my fix/feature works
• New and existing tests pass locally
• I have updated documentation if needed

[CLAassistant]

All committers have signed the CLA.

[ixchio]

Hey @Dev-Khant @deshraj @kartik-mem0 — would appreciate a review on this fix when you get a chance!

TL;DR: AsyncMemory._create_memory was missing the text_lemmatized = lemmatize_for_bm25(data) line that exists in the sync Memory._create_memory. This silently breaks BM25 keyword search for all memories created via the async path with infer=False.

One-line fix + two regression tests. All 36 tests pass, lint clean.