buildFormatted

Builds a formatted log entry with message substitution done.

This method:

• Substitutes %s placeholders with argument values (%% becomes literal %)

• Adds template info to attributes (sentry.message.template, sentry.message.parameter.N)

• Merges custom attributes

Use this for platforms that need pre-formatted messages (Apple, Web, etc.) The timestamp is provided by the native SDK, so it's not included here.