fix(sdk): add warning when log_code can't locate any files

[umakrishnaswamy]

Description

• Fixes WB-16156

What does the PR do?
adds a warning when log_code is called in a directory with no .py files or dockerfiles

🤖 Generated by Copilot at 5163052

Add a warning for missing code files in log_code. This helps the user to know if their wandb run will not have any code or Dockerfile logged.

Testing

How was this PR tested?
run in empty directories and full directories and warning performs as expected

🤖 Generated by Copilot at 5163052

log_code warns you
No files found in the dir
Autumn of repro

[codecov]

Codecov Report

Merging #6532 (476f08b) into main (56670eb) will decrease coverage by 0.28%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6532      +/-   ##
==========================================
- Coverage   76.42%   76.15%   -0.28%     
==========================================
  Files         392      392              
  Lines       45551    45552       +1     
==========================================
- Hits        34811    34688     -123     
- Misses      10680    10804     +124     
  Partials       60       60              

Flag	Coverage Δ
unittest	80.89% <0.00%> (-0.30%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
wandb/sdk/wandb_run.py	89.75% <0.00%> (-0.11%)	⬇️

... and 16 files with indirect coverage changes