There are three rules to keep in mind when deciding where to put types in your application code.

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TypeScript introduces type argument placeholders in version 5.2, which helps with partial inference and lets the language infer types for a function. When a type is used in only one place, put it in the same file where it's used. The classic example in applications is component props.

Where To Put Your Types in Application Code

Move types shared across a monorepo to a shared package

I really don’t like to remember some words like “Colocate”.
There is only one rule:
The more common the code, the closer to the project root directory. If the common code can be used cross-project, extract them as a shared package.