[FEATURE] Bulk archive for sessions (CLI and/or UI)

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

I run an automated hourly scheduled task (thread inactivity logger) that creates a new session each run. After 30 days I have 139+ dead sessions cluttering my sidebar, almost all identical "Thread inactivity logger" runs. There's no way to archive multiple sessions at once — the sidebar only supports one-at-a-time, the CLI has no sessions subcommand, and the archive_session MCP tool doesn't actually persist (separate bug: #69638).

Proposed Solution

Any of these would work:

• CLI: claude sessions archive <id> [<id>...] or claude sessions archive --before <date> or claude sessions archive --title "Thread inactivity logger"
• UI: Multi-select + bulk archive in the sidebar
• Fix archive_session MCP tool (bug report filed separately) so scripting via claude -p becomes viable

Alternative Solutions

Tried using the archive_session MCP tool in a scripted loop — returns success but doesn't persist (#69638). No filesystem-level archive flag found to edit directly. Only other option is project purge which deletes everything.

Priority

High - Significant impact on productivity

Feature Category

Interactive mode (TUI)

Use Case Example

1. Running an hourly cron scheduled task that creates a new Claude session each run
2. After a month, 100+ dead sessions fill the sidebar
3. Want to select all sessions titled "Thread inactivity logger" and archive them in one action
4. Currently must click each one individually in the sidebar — impractical at scale