Summarizer API Preference Parameter Spec Updates

Hi everyone,

Thank you very much for the feedback on the Summarizer API preference
parameter
<https://github.com/webmachinelearning/writing-assistance-apis/issues/96>
 during last week's CG meeting
<https://github.com/webmachinelearning/meetings/blob/main/telcons/2026-04-02-cg-agenda.md>
..

I've incorporated your feedback and added clarifications to the spec via
this PR
<https://github.com/webmachinelearning/writing-assistance-apis/pull/102>.
Specifically, this update details how we handle conflicting constraints and
routing fallbacks (e.g., prioritizing functional capabilities over a
"speed" preference when necessary).

For reference, here is the original PR
<https://github.com/webmachinelearning/writing-assistance-apis/pull/98> that
added this parameter to the Writing Assistance APIs spec.

We want to ensure the CG has time to weigh in before we merge, so I would
greatly appreciate any additional reviews or comments you might have!

Best,
Jaewon