fix(suspect commits): Add commitId to RELEASE_BASED suspect commits

[nora-shap]

Problem

EventFileCommittersEndpoint uses _get_serialized_committers_from_group_owners which filters for GroupOwners with commitId in context:

owner = next(filter(lambda go: go.context.get("commitId"), group_owners), None)

RELEASE_BASED suspect commits only store suspectCommitStrategy, not commitId, so they're never displayed on the Issue detail page.

Solution

Match the SCM_BASED pattern by:

1. Tracking the highest-scoring commit for each author
2. Storing commitId in context_defaults
3. Including commitId in lookup_kwargs for proper deduplication

[linear]

RTC-1250 A release based suspect commit will never be displayed on frontend

[cursor]

Bug: Owner Duplication: Lookup Prevents Record Updates

Including commitId in lookup_kwargs prevents updating existing GroupOwner records when the same author has a new suspect commit. Instead of updating the existing owner's commitId, a new GroupOwner is created, causing duplicate owners for the same user/group combination and breaking the PREFERRED_GROUP_OWNERS limit enforcement. The lookup should match on (group_id, type, user_id, project_id, organization_id) to update existing records, not create duplicates.