Make client_id configurable

[tpoliaw]

Defaulting to numtracker is fine but for other deployments (eg system tests) the best client id may be different.

[codecov]

Codecov Report

❌ Patch coverage is 75.00000% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.87%. Comparing base (bb84deb) to head (f5eed26).

Files with missing lines	Patch %	Lines
src/client/cli_auth.rs	0.00%	7 Missing ⚠️
src/client/mod.rs	0.00%	6 Missing ⚠️
src/client/config.rs	94.11%	3 Missing ⚠️
src/cli/mod.rs	85.71%	1 Missing ⚠️
src/main.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #295      +/-   ##
==========================================
+ Coverage   79.34%   79.87%   +0.52%     
==========================================
  Files          13       13              
  Lines        2116     2176      +60     
==========================================
+ Hits         1679     1738      +59     
- Misses        437      438       +1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.