add token count at status bar in real-time

[Artenx]

Displaying the real-time token count of the current conversation in the TUI status bar, this helps users check if they are approaching the model context limit.

[Hmbown]

@Marten2016 let me see what I can do about this with the deepseek api - thank you!

[LIYUE1918]

#1756

[LIYUE1918]

#1753

[richardchen874-sys]

This would be a very useful feature for DeepSeek TUI users.
@Artenx

Real-time token count is not only a UI improvement — it helps users understand when a conversation is getting close to the context limit, and it also makes long-session cost easier to reason about.

A few details could make it more helpful:

• current input/context token estimate
• remaining context window
• estimated output token budget
• warning when the session is close to the limit
• optional per-turn token usage after the API response
• maybe a compact “session total” for longer coding/chat workflows

For DeepSeek TUI, this could reduce confusion between “the model is worse now” and “the context is overloaded.” It would also help experienced independent developers manage long conversations more deliberately instead of only noticing the problem after responses start degrading or failing.