Feature: Per-terminal session affinity for --continue

Problem

When using --continue, Claude Code resumes the most recently active session globally. This causes friction for users with multiple long-running terminal sessions:

1. User has a long-running Claude session in Terminal A
2. Other Claude sessions occur in Terminals B, C, D
3. User needs to restart Terminal A's session (e.g., to pick up config changes)
4. --continue resumes the wrong session (most recent globally, not Terminal A's session)

The /resume list becomes unwieldy with many sessions, and while users can specify a session ID explicitly, this is high-friction and users often don't discover the session is "stale" until after attempting to continue.

Proposed Solution

Add per-terminal session affinity for --continue. The goal: when a user types --continue in a terminal, it should resume the session that was last active in that specific terminal, not globally.

Example Implementation Approach

One possible approach: persist session-to-terminal mappings using a "best available terminal identifier" pattern. Claude Code may have other internal mechanisms that could achieve the same goal.

On session exit: Store a mapping from terminal identifier → session ID

On --continue (without explicit session): Check for a stored mapping for the current terminal identifier before falling back to global recency

Terminal identifier priority list (use best available):

| Priority | Identifier | Source | Notes |
|----------|-----------|--------|-------|
| 1 | $ITERM_SESSION_ID | iTerm2 | Unique per tab, survives splits |
| 2 | $KITTY_WINDOW_ID | Kitty | Unique per window |
| 3 | $WT_SESSION | Windows Terminal | Session GUID |
| 4 | $TERM_SESSION_ID | macOS Terminal.app | Per-window |
| 5 | $TMUX + $TMUX_PANE | tmux | Survives detach/reattach |
| 6 | $STY + window | GNU Screen | Screen session identifier |
| 7 | tty output | Universal fallback | Recycled on terminal close |

Storage format (example):

{
  "identifier_type": "KITTY_WINDOW_ID",
  "identifier_value": "12345",
  "session_id": "abc-def-123",
  "timestamp": "2025-01-16T..."
}

Edge case - TTY recycling: For the TTY fallback (which gets recycled when terminals close/reopen), add a staleness check (e.g., ignore mappings older than 24 hours).

User Experience

Before: User must remember session IDs or scroll through /resume to find the right session

After: --continue "just works" - it continues whatever session was last active in this terminal, regardless of activity in other terminals

Notes

• The above is one possible implementation approach - Claude Code may have other internal mechanisms that could achieve the same goal more elegantly
• The identifier list is extensible as terminal emulators add new session identifiers
• Falls back gracefully: terminals without recognized identifiers behave as today (global recency)
• No breaking changes to existing behavior