[ML-931] docs: align docs with implementation

[kxzk]

TL;DR

Why

Checklist

• Has label
• Has linked issue
• Tests added for new behavior
• Docs updated (if user-facing)

Closes #

Summary

• Align docs with implementation for prompt fallback typing and SWR configuration guidance.
• Remove ambiguous default-selection wording and make explicit production-label guidance clearer.

Fixes Addressed

• docs/CACHING.md: removed incorrect "auto-set" wording for cache_stale_ttl.
• docs/API_REFERENCE.md: corrected get_prompt fallback type to include chat fallback arrays.
• docs/PROMPTS.md: clarified unlabeled selection as API-defined and explicit-label best practice.

Validation Checklist

• Langfuse CLI capability check (npx langfuse-cli api __schema)
• Langfuse prompts get contract check (npx langfuse-cli api prompts get --help)
• bundle exec rspec (blocked locally: Bundler executable mismatch)
• bundle exec rubocop (blocked locally: Bundler executable mismatch)

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[linear]

ML-931 docs: align docs with implementation

[greptile-apps]

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[Copilot]

Pull request overview

This PR updates the Ruby SDK documentation to accurately reflect current runtime behavior for prompt selection defaults, prompt fallback typing (including chat fallbacks), and SWR caching configuration.

Changes:

• Clarifies that omitting version/label uses Langfuse API default selection (not a guaranteed production label).
• Updates get_prompt docs to reflect fallback can be String (text) or Array<Hash> (chat).
• Adjusts caching guidance to remove misleading “auto-set” wording around cache_stale_ttl.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
docs/PROMPTS.md	Updates best-practice guidance to recommend explicit production labels and treats implicit selection as API-defined.
docs/CACHING.md	Removes incorrect implication that cache_stale_ttl is auto-set; frames it as an explicit, common default.
docs/API_REFERENCE.md	Corrects get_prompt parameter typing/docs and example wording around API default selection.

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 1 additional finding.