Move LLM evaluation docs to Investigate - #39522

What does this PR do? What is the motivation?

Motivation: Agent Observability evaluation docs should be discoverable from Investigate, where users look for evaluation results while troubleshooting LLM applications. The Evaluation Developer Guide also needed a visible navigation entry after the evaluations section moved.

Changes:

• Moved the English evaluation docs from hugo/content/en/llm_observability/configure/evaluations to hugo/content/en/llm_observability/investigate/evaluations.
• Reparented Evaluations under Investigate in hugo/config/_default/menus/main.en.yaml and added Evaluation Developer Guide to the Evaluations nav group.
• Updated English LLM Observability links to the new /llm_observability/investigate/evaluations paths.
• Added aliases for the former /llm_observability/configure/evaluations URLs so existing links continue to redirect.
• Removed Evaluations from the Configure landing page.

Testing:

• Parsed hugo/config/_default/menus/main.en.yaml with Ruby YAML.
• Parsed front matter for hugo/content/en/llm_observability/**/*.md with Ruby YAML.
• Ran a local route check for /llm_observability/investigate/evaluations links against English content files and aliases.
• Attempted /usr/local/hugo/bin/hugo -s hugo -d /tmp/dd-docs-public --environment development --logLevel info, but the build could not download github.com/DataDog/websites-modules from the sandbox proxy.

Merge readiness

• Ready for merge

For Datadog employees:

AI assistance

Used Bits Code powered by Codex CLI to update the docs IA, links, aliases, and navigation, then run local validation.

Additional notes

The full Hugo build should be rerun in CI or an environment with access to the Hugo module dependencies.

PR by Bits - View session in Datadog

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