docs: add Fathom to Observability (Evaluation & Quality Assurance) (#7246)

[ERA-Fathom]

This adds a documentation page for Fathom under Observability, in the Evaluation & Quality Assurance group.

Fathom 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 fathom-read package (MIT) ships a FathomListener for the CrewAI event bus. The page shows the two-line capture and the fathom read events.json --format crewai command, with an example verdict drawn from the coherence census.

What changed

• New page docs/edge/en/observability/fathom.mdx.
• A Fathom card in the Evaluation & Quality Assurance group on overview.mdx, linking to the new page.

A note on the sidebar

The nav entry belongs in docs/docs.json, but that file is 2.3 MB, past GitHub's web-editor size limit, so I could not add the line through the browser. It goes under the Observability group, right after edge/en/observability/datadog, as edge/en/observability/fathom. Glad to add it however you prefer.

Links

• fathom-read, https://github.com/ERA-Fathom/fathom
• Coherence census, https://github.com/ERA-Fathom/coherence-census

[github-actions]

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📥 Commits

Reviewing files that changed from the base of the PR and between 92eb5f9 and 4e416c4.

📒 Files selected for processing (2)

• docs/edge/en/observability/fathom.mdx
• docs/edge/en/observability/overview.mdx

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📝 Walkthrough

Walkthrough

Changes

Fathom observability documentation

Layer / File(s)	Summary
Document and index Fathom docs/edge/en/observability/fathom.mdx, docs/edge/en/observability/overview.mdx	Adds documentation for fathom-read, including findings, FathomListener event capture, CLI options, and exit codes. Adds a Fathom card that links to the new page.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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