Support Ollama image generation as a built-in tool

[ggozad]

Built-in generate_image tool. Delegates to Ollama's /api/generate with image-generation models (x/z-image-turbo, x/flux2-klein, …)

Configure the default model with OTERM_OLLAMA_IMAGE_MODEL or override per call via the tool's model argument.

Closes #302

[ggozad]

@jlbeard84 Can you please confirm if this works for you?
On my Mac image generation models do not work, presumably due to ollama/ollama#15999, ollama/ollama#15882

EDIT: Downgraded to 0.22.1 and works great.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (c0664a3) to head (44a2d70).

Additional details and impacted files

@@            Coverage Diff            @@
##              main      #306   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           32        33    +1     
  Lines         2193      2229   +36     
  Branches       275       281    +6     
=========================================
+ Hits          2193      2229   +36     

☔ View full report in Codecov by Sentry.
📢 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.