fix(ui): fix code editor error and annotations gadgets layout shifts - #10969

Description

The inline error and annotation gadgets currently rebuild through an unconditional 100 ms timeout. This makes the editor render first and then visibly shift when the gadgets appear.

This PR watches the code editor file loading state and renders gadgets synchronously at the same phase as code mirror initial render. The trace gutter already uses this pattern by watching the same loading state and updating synchronously.

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