Regression: session display name not set in terminal title and /resume list (v2.1.168)

@## Description

Since v2.1.168 (built 2026-06-06), the auto-generated session display name is no longer shown in the terminal window title or the /resume session picker.

Expected Behavior

1. Terminal window title: Shows the auto-generated session display name (e.g., "hidden-plotting-jellyfish")
2. /resume list: Shows auto-generated session names or AI-summarized titles

Actual Behavior

1. Terminal window title: Always shows "Claude Code"
2. /resume session picker: Shows the lastPrompt value (the last user message) as the session name instead of an auto-generated display name

Evidence

• The \slug\ field (e.g., \playful-sniffing-rain\, \hidden-plotting-jellyfish\) is still being generated and stored in the session JSONL files
• The session metadata files in \~/.claude/sessions/*.json\ lack a \name\ field unless manually set via \/rename\
• Running with \claude --name "test"\ works correctly — the name is shown in the prompt box, terminal title, and /resume picker

Steps to Reproduce

1. Start a new session with \claude\
2. Send any message
3. Open the terminal window title — shows "Claude Code"
4. Exit and run \claude /resume\ — sessions show the last message content instead of auto-generated names

Environment

• Claude Code version: 2.1.168
• Platform: Windows 11 (win32)
• Terminal: Windows Terminal
• Shell: PowerShell/bash
• API: Third-party proxy via ANTHROPIC_BASE_URL

Related

The \--name\ flag description says: "Set a display name for this session (shown in the prompt box, /resume picker, and terminal title)" — this works when used explicitly, but the auto-naming (which previously populated this field) no longer does so.

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