feat(eval): multi-model comparison, gd-eval models command, Langfuse …

[zdenekmusil-gd]

…enhancements

Multi-model comparison (--model repeated):

• gd-eval run --model gpt-5.2 --model gpt-4o evaluates the full dataset against each model sequentially and prints a side-by-side comparison table with winner. --model accepts provider/model syntax to disambiguate .
• --provider flag removed — superseded by provider/model syntax; ambiguous-model error now suggests the syntax directly.
• Workspace original active model restored in finally block after all models run.
• JSON report always uses nested {models, runs, comparison} shape.
• Langfuse: one named dataset run per model (gd-eval-{ts}-{model_id}).

New command: gd-eval models

• Lists all LLM providers and their models with provider ID, family, and active marker. Marks the workspace's currently active model when --workspace given.

Provider type labelling:

• Always fetches model family live via list_llm_provider_models_by_id() — automatically correct for new families without code changes.
• Combines gateway + family: OPENAI→family only, AWS_BEDROCK→BEDROCK/family, AZURE_FOUNDRY→AZURE/family (e.g. BEDROCK/ANTHROPIC, AZURE/OPENAI).
• Model and provider_type in Langfuse trace metadata, tags, and dataset-run-item runDescription + metadata.

EvalReport gains provider_name and provider_type; comparison table shows provider/model to distinguish runs with the same model id across providers.

JIRA: GDAI-1831
Risk: low — new isolated features; no changes to existing packages.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.10%. Comparing base (c028c31) to head (c253bdf).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1642   +/-   ##
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  Coverage   79.10%   79.10%           
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  Files         231      231           
  Lines       15718    15718           
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  Hits        12433    12433           
  Misses       3285     3285           

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