Make /resume session limit configurable in settings.json

Summary

The /resume picker is hardcoded to show a maximum of 50 sessions. Power users who accumulate many sessions need to scroll through or remember session names to find older ones.

This was previously tracked in #48207, which was auto-closed by a stale bot without developer review.

Why this matters now

As of v2.1.113, Claude Code switched from node.exe cli.js to a compiled SEA binary (claude.exe). The JS source files are no longer shipped in the package, so the previous workaround of patching the hardcoded limit in the minified bundle is no longer possible.

Proposed solution

Expose a configurable session limit in settings.json:

{
  "resume": {
    "maxSessions": 200
  }
}

The default can remain 50. The limit is already a default parameter in the session-loading functions — making it configurable should be a minimal change.

Context

• The limit variable was previously patchable in the minified cli.js (a single =50 constant)
• v2.1.113 removed cli.js entirely in favor of bin/claude.exe (SEA binary)
• There is no settings.json key or CLI flag to override this limit
• Related: #48207 (auto-closed without review)