This PR changes the status code behavior for errors to attempt to return more specific status codes when possible while still striving for exhaustive error responses. As can be seen in the README, the new flow is:

flowchart TD
	Request[Request has errors?] -->|yes| Panic
	Request -->|no| Continue[Continue to handler]
	Panic[Panic?] -->|yes| 500
	Panic -->|no| RequestBody[Request body too large?]
	RequestBody -->|yes| 413
	RequestBody -->|no| RequestTimeout[Request took too long to read?]
	RequestTimeout -->|yes| 408
	RequestTimeout -->|no| ParseFailure[Cannot parse input?]
	ParseFailure -->|yes| 400
	ParseFailure -->|no| ValidationFailure[Validation failed?]
	ValidationFailure -->|yes| 422
	ValidationFailure -->|no| 400

The change is fairly small & unobtrusive. Several tests have been updated to reflect the changes. It should not break clients, however your API will have new documented responses when upgrading Huma.

Note: the above flowchart deliberately excludes stuff like 405 Method Not Allowed because that returns at the low-level router before any of the above executes.