Say how big a session is before it is imported

The import list reported a line count, which is the wrong axis: these
transcripts embed screenshots as base64, so one line can be a megabyte.
On this machine a 69 MB session has 3,427 lines while a 44 MB one has
6,792 — the number on the row said nothing about what continuing the
session would cost, and size is the only thing there that predicts it.
The session behind the 2026-08-29 incident was 65 MB across 13,000 lines,
a line count that looks unremarkable.

Shown beside the line count rather than instead of it, since a short file
of long lines is exactly the expensive case. Not warned about and not
marked: importing a large session is a choice somebody is entitled to
make, and flagging it would be the interface nagging about a decision
already taken.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VETa8afmpWaYezLCqJhDB8

AGENTS.md

@@ -272,6 +272,13 @@ day:
 - Local only: an ssh session's child dies with its connection, so it takes
   the ordinary `--resume` path.
 
+The import list reports each session's **size as well as its line count**,
+because the two disagree in the way that matters: these transcripts embed
+screenshots as base64, so one line can be a megabyte. On this machine a
+69 MB session has 3,427 lines and a 44 MB one has 6,792 — nothing about a
+line count tells you what continuing a session will cost. Shown, not warned
+about; importing a large session is a choice somebody is entitled to make.
+
 **Never import a Claude Code session that is open in a terminal.** The app
 refuses it now — it reads `~/.claude/sessions/<pid>.json`, which Claude
 Code keeps for every live session, and checks the pid's start time so a