[FEATURE] Docs: add Fathom to the Observability section

Feature Area

Documentation

Is your feature request related to a an existing bug? Please link it here.

NA. This is a documentation addition, not tied to an existing bug.

Describe the solution you'd like

Add a documentation page for Fathom in the Observability section, under Evaluation & Quality Assurance.

Fathom (fathom-read, MIT) is a deterministic read over the events a CrewAI crew already emits. It folds the successful tool calls and task completions into the crew's committed state and names the step where a later action contradicts an earlier one. It needs no model access and runs after a crew finishes, on a file you already have. The package ships a FathomListener for the CrewAI event bus.

The page fits alongside the existing observability integrations (Patronus, Langfuse, Arize Phoenix, and others). PR #7245 implements it: a new docs/edge/en/observability/fathom.mdx and a Fathom card on the Observability overview.

Describe alternatives you've considered

None. This follows the pattern of the existing observability integration pages.

Additional context

Implemented in PR #7245. The sidebar entry in docs.json is called out separately in that PR because the file is 2.3 MB, past GitHub's web-editor size limit.

Willingness to Contribute

Yes, I'd be happy to submit a pull request

Start by reviewing PR #7245 and the existing observability integration pages. Check docs/edge/en/observability/fathom.mdx, the Observability overview card, and the separately handled docs.json sidebar entry; done means the Fathom page, card, and navigation entry are present and follow the established documentation pattern.