Mobile: keep agent sessions warm (or pre-warm on connect) and show the context window meter on the phone

[EdwinMisael]

Two asks from using the iOS app against a self-hosted server (t3 0.0.38 on Linux, Claude provider), with what I measured.

1. Keep agent sessions warm longer, or pre-warm on connect.
ProviderSessionReaper stops any idle session after 30 minutes (DEFAULT_INACTIVITY_THRESHOLD_MS), and server.ts passes no options, so the threshold cannot be changed. From a phone, gaps between messages are usually longer than 30 minutes, so almost every message pays a cold start. On my server (an older 4-core box) the Claude process takes about 8.7 s to start before it resumes the transcript or calls the model, and after an idle hour the provider also rebuilds its prompt cache. Asks: a server setting for the threshold, and a pre-warm step that starts the resume handshake when a mobile client opens a thread whose session is stopped, instead of waiting for the first message. Related: #9586 covers a different side effect of the same reaper.

2. Context window meter on mobile.
The web client has ContextWindowMeter in the chat view. The mobile app has no equivalent, so on long threads from the phone there is no way to see how full the context is. Ask: port the meter to the mobile thread screen. A compact number is enough. #6220 asked for this as an issue and was closed; filing it here as an idea per CONTRIBUTING.

[juliusmarminge]

Closing as a duplicate of existing open ideas:

1. Configurable reaper / keep sessions warm → #7018 (server setting for ProviderSessionReaper inactivity threshold). Related bug side-effect: #9586.
2. Context window meter on mobile → #6954 (port of web ContextWindowMeter; same ask as closed #6220).

Please continue / upvote there. Happy to reopen if something here is distinct beyond those two.