Covers list_pull_requests, pull_request_read, pull_request_write, and
pull_request_review_write, split out of the flat plugins/bin/skills/gitea
PR-dispatch logic per ADR 0011. Composes gitea-labels-milestones for
label/milestone ID resolution instead of duplicating that lookup.
Tool signatures were cross-checked live via ToolSearch against the deployed
gitea-mcp server rather than copied from api-reference.md, per the ADR's
schema-drift mitigation process.
