DOC/DEV: rework delegation guidance (#903)

Author: lucascolley

docs/contributing.md

@@ -49,8 +49,8 @@ pixi shell --environment=dev
 
 - [Open an issue](https://github.com/data-apis/array-api-extra/issues/new) to
   propose the new function. You may want to wait for initial feedback on the
-  issue before diving into an implementation. Feel free to skip this step if
-  there is already an open issue for the function.
+  issue before diving into an implementation.
+  Skip this step if there is already an open issue for the function.
 - Add the implementation of your function to
   `src/array_api_extra/_lib/_funcs.py`.
   - Ensure that your function includes type annotations and a
@@ -62,31 +62,27 @@ pixi shell --environment=dev
   - Ensure that `lazy_xp_function` is called on the function if lazy backends
     are supposed to be tested.
 - Add your function to `docs/api-reference.md`.
-- [Make a PR!](https://github.com/data-apis/array-api-extra/pulls)
-
-## How to add delegation to a function
+- Don't worry if you are not sure how to do some of the above steps or think you
+  might have done something wrong -
+  [make a PR!](https://github.com/data-apis/array-api-extra/pulls)
 
-See [the tracker for adding delegation][delegation-tracker].
+### Delegation
 
-[delegation-tracker]: https://github.com/data-apis/array-api-extra/issues/100
+Many new functions should also have 'delegation' to existing implementations in
+known array libraries added. This can happen in the same PR which adds the function,
+or in a follow-up PR.
 
-- If you would like to discuss the task before diving into the implementation,
-  click on the three dots next to the function on the tracker issue, and choose
-  "Convert to sub-issue".
 - Create a function in `src/array_api_extra/_delegation.py` with a signature
   matching the function in `src/array_api_extra/_lib/_funcs.py`, and move the
   docstring to the new function. Leave a one-line docstring in `_funcs.py`,
   pointing to `_delegation.py` to see the full docstring.
 - Also move the initial `array_namespace` call and any input validation over to
   the new function.
-- Add delegation to backends using the `if _delegate` pattern. See
+- Add delegation to backends using the `if_*_namespace` functions. See
   `src/array_api_extra/_lib/_backends.py` for the full list of backends we have
   worked with so far.
 - After all delegation layers, return the result from the implementation in
   `_funcs`.
 - Simplify the signature in `_funcs.py` to remove impossible arguments now that
   it is only called internally via `_delegation`. For example, the `xp`
   parameter can be changed from type `ArrayNamespace | None` to `ArrayNamespace`.
-- Don't worry if you are not sure how to do some of the above steps or think you
-  might have done something wrong -
-  [make a PR!](https://github.com/data-apis/array-api-extra/pulls)