Complete canonical agent shims and deploy contributor guidance

[devantler]

🤖 Generated by the Daily AI Assistant

Current problem

This repo needs the same canonical agent guidance and deploy contributor
documentation as the rest of the portfolio. The original June 19 scope predates
two generally available Copilot code-review changes, so its
parallel-instructions premise is now obsolete.

Draft #92 delivers the remaining canonical shims and deploy guidance.

Superseded scope

• Do not add .github/copilot-instructions.md. Copilot code review gained
  root AGENTS.md support on 2026-06-18, so the canonical file now serves that
  reviewer directly:
  https://github.blog/changelog/2026-06-18-copilot-code-review-agents-md-support-and-ui-improvements/
• Do not put repo-specific Crossplane instructions in
  .github/CONTRIBUTING.md. This repository supplies the organization-wide
  default community-health file to repositories that do not override it;
  repo-specific guidance belongs in AGENTS.md and deploy/README.md.

Acceptance criteria

• Root AGENTS.md is the canonical repo-specific instruction file with a
  ## Maintenance section.
• CLAUDE.md and GEMINI.md are one-line @AGENTS.md shims in draft docs: complete agent and deploy contributor guidance #92.
• deploy/README.md documents the OpenBao credential
  refresh/degraded-refresh behavior in draft docs: complete agent and deploy contributor guidance #92.
• deploy/README.md points contributors to the canonical authoring rules,
  exact validation command, and roadmap epic Roadmap: declarative GitHub-org-as-code — extend coverage & sustain the source of truth #56 in draft docs: complete agent and deploy contributor guidance #92.
• kubectl kustomize deploy/ > /dev/null and git diff --check pass for
  draft docs: complete agent and deploy contributor guidance #92.

Rough size

Small documentation and instruction-file completion.

[devantler]

🤖 Generated by the Daily AI Assistant

Shipped draft #59 addressing this. One scope note that revises this issue's premise:

• AGENTS.md — added (with a ## Maintenance card + the declarative/Observe-first/teams-over-individuals golden rules). ✅
• .github/copilot-instructions.md — won't-add. The root contract retired the separate Copilot-review file org-wide on 2026-06-18 (Copilot code review reads AGENTS.md directly), so a parallel file is now redundant rather than missing.
• CONTRIBUTING.md deploy/ guidance — not added to .github/CONTRIBUTING.md, because that file is the org-wide default community-health file rendered for every repo; the Crossplane authoring workflow lives in the new AGENTS.md (canonical) + the existing deploy/README.md instead.

So #59 closes the real intent of this issue. Bullets 2 and 3 are intentionally resolved as won't-do-here for the reasons above.