Duplicated jsdoc should error

It's possible to document parameters and function expressions 2-3 different places in JSDoc. However, I can't think of a good reason to do so, and I suspect that it's (1) rare (2) by mistake. Here's an example:

/** @param a - the a */
function f(/* an a */ a) {
}

Today gives the jsdoc

 an a
 - the a

But should give an a and an error on @param a: "Duplicate jsdoc".

The problem is even worse in JS, where jsdoc provides types. Here, the innermost type annotation provides the type and the rest are ignored. This should definitely be an error:

/** @param {string} a */
function f(/* @type {number} */ a) {
}

This example should have an error on @param a: "Duplicate jsdoc"

Thanks to @bterlson for this idea.

Start by tracing how TypeScript parses and merges JSDoc on parameters and function expressions, using the two examples in the issue as repro cases. Done means duplicate parameter documentation and conflicting inline type annotations produce a "Duplicate jsdoc" error while preserving the specified diagnostic behavior.