⚡ Bolt: Enable SQLite Memory-Mapped I/O in Metadata Store

[thebearwithabite]

💡 What: Replaced an invalid literal string "XXXXXXXXX" with the correct integer value 268435456 for PRAGMA mmap_size in local_metadata_store.py.
🎯 Why: SQLite configurations must use valid integer values. An invalid string causes SQLite to fail silently and disable memory-mapped I/O, negating intended performance benefits.
📊 Impact: Expected performance improvement in database read operations, enabling the 256MB memory mapping intended by the original design.
🔬 Measurement: Verify with grep that PRAGMA mmap_size is now correctly set to 268435456 in local_metadata_store.py.

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PR created automatically by Jules for task 18028057969174997367 started by @thebearwithabite

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