docs: note that closing keywords do not fire on a develop merge

[LukasWodka]

Precondition for backend#1373.

client and cli both carry this caveat in their own PR templates. It is not repo-specific — every repo targets develop, and GitHub only honours closing keywords when a PR merges into the default branch. So Closes #123 on a develop-targeted PR silently does nothing until the change is promoted to main/master.

#1373 proposes deleting the per-repo templates so the org one applies automatically. This is one of exactly two things those templates knew that the shared one did not — lifting it up first means the deletions lose nothing.

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Note

Low Risk
Documentation-only change to the PR template with no runtime or security impact.

Overview
Updates the shared Related section comment in .github/pull_request_template.md so contributors know Closes / Fixes keywords only work when merging into the default branch, not when PRs target develop.

This aligns the org template with caveats already in per-repo templates and supports consolidating templates without losing that guidance.

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[LukasWodka]

👋 Heads-up — Code review queue is at 41 / 30

Above the WIP limit. The team convention is to review existing PRs before opening new work.

Open PRs currently in Code review (oldest first):

• averaging-service#255 — chore(ci): enable Dependabot security updates · author: @LukasWodka · no reviewer assigned
• backend#1146 — docs(rfc): platform cost & autoscaling architecture · author: @saadqbal · reviewer: @LukasWodka, @saqlainsyed007, @aptracebloc
• backend#1201 — docs(rfc): Data spaces & federated dataset composition (draft) · author: @LukasWodka · reviewer: @saadqbal
• backend#1217 — docs(rfc): Dataset integrity & score reproducibility (draft) · author: @LukasWodka · reviewer: @saadqbal
• backend#1261 — RFC-BACKEND-0008: board & process reset (decision RFC — for markup) · author: @LukasWodka · reviewer: @saadqbal
• backend#1284 — docs(deploy): backend deploy runbook skeleton (#1263) · author: @LukasWodka · no reviewer assigned
• backend#1332 — feat(check-model): allow KNN/GaussianProcess on a single-edge owned dataset (#923 follow-up) · author: @divyasinghds · no reviewer assigned
• backend#1353 — chore(ci): baseline historical gitleaks findings + wire caller · author: @LukasWodka · no reviewer assigned
• backend#1361 — feat(tasks): bound ExperimentQueue growth for PAUSED experiments (backend#1351) · author: @saqlainsyed007 · reviewer: @aptracebloc
• claude-skills#14 — feat(skill): add tracebloc-frontend-app skill · author: @waqaskhanroghani · reviewer: @saadqbal

Pull from review before opening new work. (This is a nudge from the kanban WIP check, not a block.)