[LOW] Exists() error silently ignored for StatusError cards in AttachCommand

When card.Status == StatusError, the check is:

if exists, err := a.sessions.Exists(card.Session); err == nil && !exists {
    return nil, errors.New("the agent's session is gone; ...")
}

If Exists() returns (false, someErr) — for example, an unexpected tmux error string not covered by isNoSuchSession — the condition err == nil && !exists is false, so the code falls through and attempts to attach anyway. The user then receives tmux's raw error instead of the friendly message the PR intends to provide.

isNoSuchSession already handles the common "no server running" case (returning (false, nil)), so this only bites on unanticipated tmux error output. Consider returning the error explicitly when Exists() fails, e.g.:

exists, err := a.sessions.Exists(card.Session)
if err != nil || !exists {
    return nil, errors.New("the agent's session is gone; move the card forward to relaunch it, or delete it")
}

[LOW] Crash-loop counter grows unboundedly while card remains in StatusError

Once launchFailed(cardID) >= maxLaunchFailures and the card transitions to StatusError, the watcher continues to loop every cappedRetryDelay (5 s). On each iteration the pane is still dead (alive == false), so launchFailed() is called again — incrementing the counter to 4, 5, 6, … indefinitely.

The practical impact is minimal (int won't overflow in any realistic timeframe, and setStatus(StatusError) is idempotent). However, after the user triggers a prompt-bearing relaunch, resetLaunchFailures correctly clears the counter, so recovery still works. The simplest fix is to skip the launchFailed() increment when the card is already in StatusError:

if card.Status != StatusError {
    if c.launchFailed(cardID) >= maxLaunchFailures {
        c.setStatus(cardID, StatusError)
        delay = cappedRetryDelay
    } else {
        c.resume(card)
    }
} else {
    delay = cappedRetryDelay
}

Or alternatively read the card's status after the store fetch (it's already available) and bail out of the Alive/launchFailed branch early.