docs(secrets): clarify age strict mode default

[risu729]

Summary

• document that direct age encryption requires experimental features to be enabled
• clarify that age decryption is strict by default
• document that age.strict=false skips undecryptable values and continues resolving the environment

Testing

• mise run docs:build

Refs #9730

[greptile-apps]

Greptile Summary

This PR improves the age encryption documentation by adding a missing prerequisite step (enabling experimental features) to the Quick Start guide and rewriting the strict-mode section to clearly state that strict decryption is the default behavior, with explicit instructions for disabling it.

Confidence Score: 5/5

Documentation-only change with no runtime impact; safe to merge.

The change touches only a single Markdown documentation file. The new content accurately reflects the experimental gating requirement and the strict-by-default decryption behavior, correcting a previously ambiguous description. No code paths are modified.

No files require special attention.

Important Files Changed

Filename	Overview
docs/environments/secrets/age.md	Documentation update: adds 'enable experimental features' as step 1 in Quick Start, renumbers subsequent steps, and replaces the ambiguous single-line note about non-strict behavior with a clear explanation that strict mode is the default and how to disable it.

_{Reviews (3): Last reviewed commit: "docs(secrets): clarify age decryption st..." | Re-trigger Greptile}

[gemini-code-assist]

Code Review

This pull request updates the documentation for age-encrypted secrets to include instructions for enabling experimental features and to reflect changes in decryption behavior, which is now strict by default. The review feedback suggests using the explicit set subcommand for consistency, refining the technical description of strict mode to focus on decryption, and standardizing the syntax for setting configuration values.