Memory import broken when starting a new chat — messages not summarized, ghosted incorrectly

[marz-fck]

I ran into an issue when trying to transfer memory from one chat to a new one using the Export/Import feature.
Steps to reproduce:

1. Have a long chat (~300 messages) with Summaryception active and memory built up
2. Export memory as JSON
3. Start a brand new chat with the same character
4. Import the exported memory into the new chat
   The extension does nothing. It reports no new messages to summarize, even though the new chat has messages in it.
   Root cause (after manual investigation of the .jsonl file): The import carries over state that is tied to the old chat, which breaks the new one in several ways:

• summarizedUpTo remains at the old chat's message count (e.g. 330), so the extension thinks everything is already processed
• ghostedIndices contains indices from the old chat that collide with indices in the new chat (0, 1, 2… overlap), causing new messages to be treated as already ghosted
• Some snippets in Layer 0 / Layer 1 have turnRange: [0, 4] from a partial summarization that happened in the new chat before the import — this further confuses the state
• all messages in the new chat have sc_ghosted: true and is_system: true set directly in their message bodies, making them invisible to the extension
  I had to manually fix all of these fields in the .jsonl file to get it working.

[Lodactio]

I'll take a look into this