chore: update fullsend shim workflow

[fullsend-ai-fullsend]

This PR updates the fullsend shim workflow to match the current template in the .fullsend config repo.

The shim content has drifted from the template — this brings it back in sync.

[fullsend-ai-retro]

🤖 Finished Retro · ✅ Success · Started 7:08 PM UTC · Completed 7:15 PM UTC
Commit: d8b1c3d · View workflow run →

[fullsend-ai-retro]

Retro: PR #2 — chore: update fullsend shim workflow

Workflow went well — no new proposals.

This was a bot-generated onboarding PR (fullsend/onboard branch) by fullsend-ai-fullsend[bot] that synced the .github/workflows/fullsend.yaml shim with the upstream template. It was merged immediately by ggallen with no code agent involvement, no review findings, and no rework cycles. The workflow was clean and efficient.

Observation: this retro run was itself low-value

The main finding is that dispatching a retro agent on a trivial bot-authored infrastructure PR is wasteful. However, this is already well-known and extensively tracked:

• Open issues: #2461 (skip retro for autoclosed bot PRs), #2638 (skip retro for merged bot PRs with no review findings), #939 (skip retro on PRs with no agent involvement), #1630, #2708
• Recently closed: #2590 (retro skip guard for onboarding PRs is not effective), #1713 (retro agent should skip bot-authored onboarding/infrastructure PRs)

All potential proposals from this retro are already covered by existing issues. No new proposals filed.