The v2 context meter could only show token counts after a compaction had
already happened — v2 had no live usage plumbing at all, so main's
compaction-threshold UX was invisible on v2 threads. Provider turns now
carry an optional tokenUsage report: the Codex adapter maps the
app-server's thread/tokenUsage/updated notification (total breakdown +
model context window) onto the active provider turn, ChatView picks the
newest report out of the projection, and the meter prefers it over the
compaction fallback — so usage and remaining-context percentages update
while the turn runs.

Claude's v2 adapter does not report usage yet; its meter falls back to
compaction items as before.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>