[Bug] Custom session names lost - showing first message instead of renamed titles

Bug Description

All custom session names have been wiped/lost. The session picker now shows the raw first message content instead of the user-assigned names.

This is data loss - users who meticulously rename their sessions to organize their work have lost all that metadata.

Environment

• Platform: Windows 11
• Version: 2.1.29
• Terminal: Windows Terminal

Screenshot

Session picker showing first-message content like:

• "Launch an agent to give you an overview of D:\OneDrive..."
• "<command-message>task</command-message>..."
• "i got a message from the md of align that theyre..."
• "See a task I've been given: compile a list of..."

Instead of the custom names the user assigned via Ctrl+R rename.

Expected Behavior

Custom session names should persist and display in the session picker.

Actual Behavior

• All custom names are gone
• Sessions now show truncated first-message content
• No way to identify sessions by their purpose/topic
• User's organizational work is lost

Impact

• Data loss - custom names are gone
• Sessions become unidentifiable
• Power users who rely on naming conventions can't find their work
• Defeats the purpose of the rename feature

Possibly Related

This may be related to:

• #22741 (session fragmentation bug reported same day)
• Potential migration/schema change in 2.1.29 that didn't preserve name field

Questions

1. Are the names still in session files but UI not reading them?
2. Was there a schema migration that dropped the name field?
3. Is there a way to recover the names from backup/previous session format?