[FEATURE] prompt for `cleanupPeriodDays` during initial setup

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

Summary

The cleanupPeriodDays setting auto-deletes session history after 30 days by default, but most users never learn it exists until they lose work. Since deletion is irreversible and there's no interactive way to recover a swept session, the initial setup flow should surface this setting and let the user choose a retention value up front. This affects the CLI/console as well as the VS Code extension (see related #79122).

Motivation

• The 30-day default is too small for long-lived projects or sessions set aside for a while, and it's applied silently.
• Deletion is irreversible — once the .jsonl is gone there's no trace it ever existed, and the --resume picker offers no recovery.
• Today the only way to discover cleanupPeriodDays is to already know it exists and hand-edit settings.json. By the time a user goes looking, they've usually already lost something. Presenting it during setup removes the need for any separate warning later.

Proposed Solution

During initial Claude Code setup (first run / onboarding), ask the user to choose how long sessions are kept, e.g.:

Session history is auto-deleted after a period of inactivity.
How long should sessions be kept?
  [1] 30 days (default)
  [2] 90 days
  [3] 1 year
  [4] Keep forever (never auto-delete)
  [5] Custom (enter number of days)

• "Keep forever" writes a very large value (JSON has no infinity), e.g. 999999999.
• The chosen value is written to ~/.claude/settings.json.

Alternative Solutions

Workaround (today)

Set a large retention manually in ~/.claude/settings.json:

 {
   "permissions": {
     "allow": [
       "Bash"
     ]
   },
   "theme": "dark",
-  "autoCompactEnabled": true
+  "autoCompactEnabled": true,
+  "cleanupPeriodDays": 999999999
 }

Takes effect on the next claude startup.

Priority

High - Significant impact on productivity

Feature Category

CLI commands and flags

Use Case Example

_No response_

Additional Context

Environment

• Claude Code version: 2.1.198
• Platform: Linux (CLI / console); also affects VS Code extension

Related

• #79122 — silent 30-day cleanup deletes content of still-open sessions (framed around VS Code; same cleanupPeriodDays behavior, also affects the CLI).