Fix release drafter empty changelogs and render stale branch refs

[milldr]

What

• Add 10s delay to release-drafter workflow to avoid GitHub GraphQL API race condition
• Add workflow_dispatch trigger for manual re-runs when drafts are empty
• Add autolabeler config to auto-label PRs from branch name patterns
• Fix flow render to use origin/<default> instead of local branch ref when creating new branches
• Add test verifying new branches use the remote ref as start point

Why

Release drafter was intermittently producing empty changelogs ("No changes") because its GraphQL query for associated pull requests ran before the API had propagated the commit/PR association (~9s after push). Traced through the release-drafter v6 source to confirm the query uses history(since:) with associatedPullRequests, which is subject to eventual consistency.

Separately, flow render was creating new branches from potentially stale local refs in the bare repo cache. After fetch --all, the remote tracking refs (origin/main) are updated but the local branch ref (main) may still point to an old commit.

Ref

• Release drafter source: lib/commits.js — findCommitsWithAssociatedPullRequestsQuery
• Affected releases: v0.3.0, v1.4.0, v1.5.0 all showed "No changes"
• Working releases (v1.1.0–v1.3.0) either had accumulated drafts or got lucky with API timing