[Fix] Gitea tasks use GitHub usernames for PR assignment

[roomote-roomote]

​Opened on behalf of @daniel-lxs. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Resolve a selected repository's source-control provider and linked identity from its exact full name and payload host.
• Preserve stamped provider and host attribution for homogeneous ALL_REPOSITORIES tasks without querying the aggregate sentinel as a repository.
• Stamp aggregate provider coverage so missing, host-ambiguous, mixed, or conflicting selections fail closed before identity lookup.
• Cover same-name repositories across hosts, homogeneous aggregate assignment, and incomplete aggregate selections with focused regression tests.

Why this change was made

Workspace-wide provider stamps can describe a primary repository rather than the repository receiving a pull request. Aggregate selections also need to retain their safe stamped attribution path without treating partial repository resolution as homogeneous.

Impact

PR attribution and assignment now follow the exact target repository provider and host, while fully resolved homogeneous all-repository tasks retain their linked provider identity. Ambiguous, incomplete, and mixed-provider selections fall back to Roomote attribution without a user assignee.

[roomote-community]

No new code issues found. See task

• Resolve PR attribution from the target repository's exact provider and host.
• Fail closed when an ALL_REPOSITORIES selection contains a missing or ambiguous repository mapping.
• Preserve host-scoped linked attribution for homogeneous ALL_REPOSITORIES tasks (packages/cloud-agents/src/server/task-run-queue.ts:2053).

_{Reviewed 0d5f4db}

[roomote-roomote]

Fixed in 627fa9b: homogeneous aggregate tasks now stamp their single unambiguous source-control host during enqueue, while mixed-provider and multi-host workspaces keep host attribution unset. The enqueue regression test carries the persisted payload through the aggregate resolver used by prompt attribution. Seven provider-stamping tests and eight aggregate resolver tests pass, package TypeScript and changed-file lint checks pass, and the full pre-push gates pass. See task