[BUG] "wrote N memories" count in status line is always N+1

Description

When Claude saves memories, the status line overcounts by 1. Writing 1 memory shows "wrote 2 memories" because updating the MEMORY.md index file is also counted as a memory write.

Steps to Reproduce

1. Ask Claude to remember something (triggers a single memory save)
2. Status line shows "wrote 2 memories" instead of "wrote 1 memory"

Expected Behavior

Count should exclude the MEMORY.md index update. 1 memory written → "wrote 1 memory".