feat(chat ui): improve /context ui

[GoodluckH]

• Reworded things to make it less confusing about what /context is for.
  • Users are adding "rules", not really "files" to the context. That had been made clear in this PR.
• Added token count est for each file

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 22.34043% with 73 lines in your changes missing coverage. Please review.

Project coverage is 13.70%. Comparing base (e0f65f3) to head (214edd3).
Report is 426 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/q_cli/src/cli/chat/mod.rs	0.00%	46 Missing ⚠️
crates/q_cli/src/cli/chat/context.rs	39.39%	17 Missing and 3 partials ⚠️
crates/q_cli/src/cli/chat/command.rs	0.00%	7 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##             main    #1147    +/-   ##
========================================
  Coverage   13.69%   13.70%            
========================================
  Files        2361     2362     +1     
  Lines      203706   203886   +180     
  Branches   184070   184250   +180     
========================================
+ Hits        27894    27933    +39     
- Misses     174425   174562   +137     
- Partials     1387     1391     +4     

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