enable pull request limits

[don-petry]

https://github.blog/open-source/maintainers/how-pull-request-limits-are-cutting-down-the-noise/

[don-petry]

📋 Initiative planned by the BMAD Scrum Master (Bob).

Epic #505 — Enable GitHub pull request limits to cut automation-PR noise

5 stories created (inert — labelled initiative, NOT initiative:auto):

• [Phase 1] ADR: pull-request-limits mechanism + policy decision #506 (M) — [Phase 1] ADR: pull-request-limits mechanism + policy decision
• [Phase 2] Encode the PR-limit configuration in the apply mechanism + tests #507 (M) — [Phase 2] Encode the PR-limit configuration in the apply mechanism + tests
• [Phase 3] Apply path: enforce the limit on target repo(s) + tests #508 (M) — [Phase 3] Apply path: enforce the limit on target repo(s) + tests
• [Phase 3] Document the PR-limits standard + exemption rationale #509 (S) — [Phase 3] Document the PR-limits standard + exemption rationale
• [Phase 4] Measure the noise reduction (success-metric instrumentation) #510 (M) — [Phase 4] Measure the noise reduction (success-metric instrumentation)

Open questions for review:

• What is the final numeric pull-request limit, and which actors are exempt (e.g. first-party automation: dev-lead, auto-rebase, Dependabot)? Story 1 proposes candidates and the config is built parameterized; a human must confirm the value and exemption list before Story 3 enforces it on a live repo.
• What is the rollout scope - pilot the limit on a single repo (e.g. .github-private) first, or roll out org-wide via the central petry-projects/.github standards repo? This determines the apply path's target scope (Story 3) and the report's coverage (Story 5).
• [reviewability] All story references resolve in the .github-private checkout the planner used, but the planning context's repo is petry-projects/.github and that is where apply-plan.sh materializes the epic. Confirm which repo the automation scripts (apply-repo-settings.sh, list-prs.sh, .github/rulesets/) actually live in / will be edited in, so stories do not point dev-lead at paths absent in the target repo.

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Review the epic and its sub-issue DAG, adjust as needed, then add initiative:auto to epic #505 to hand it to initiative-driver for auto-implementation.