docs: clarify trace retention behavior

[sineha-mani]

Summary

• Clarify when feedback, evaluators, automation rules, and annotation queue operations can extend trace retention.
• Update stale docs that said all annotation queue adds and multi-turn evaluators automatically upgrade traces.
• Document that manual UI feedback/notes and manual annotation queue adds do not change retention by default, while SDK/API feedback may still extend retention unless opted out.

Test Plan

• Docs-only change; reviewed rendered Markdown diff locally.

[github-actions]

Thanks for opening a docs PR, sineha-mani! When it's ready for review, please add the relevant reviewers:

• @katmayb or @fjmorris (LangSmith)

[github-actions]

Mintlify preview branch generated: preview-sineha-1783732909-9486b1c

Site preview: https://langchain-5e9cc07a-preview-sineha-1783732909-9486b1c.mintlify.app

Important

Preview links may take a few minutes to start working while the deployment finishes.

Changed documentation pages (preview deep links):

• src/langsmith/usage-and-billing.mdx
• src/langsmith/annotation-queues.mdx
• src/langsmith/rules.mdx
• src/langsmith/evaluators.mdx
• src/langsmith/annotate-traces-inline.mdx

Only the top 5 changed markdown files by diff size are listed.