docs: add AGENTS.md and CONTRIBUTING.md (GRO-2381) (#215)

Co-authored-by: Flea Flicker <22+gb_flea@noreply.git.farh.net>
Co-committed-by: Flea Flicker <22+gb_flea@noreply.git.farh.net>

AGENTS.md

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+# AGENTS.md
+
+This repository (`groombook/api`) is part of the GroomBook application stack. The
+authoritative process, quality bar, and safety rules live in the shared
+[`groombook/org`](https://git.farh.net/groombook/org) skills repository. Read
+those first; this file is only a pointer.
+
+## Authoritative skills
+
+- **SDLC (branching, PRs, phases, handoffs):**
+  [`groombook/org/skills/sdlc/SKILL.md`](https://git.farh.net/groombook/org/src/branch/main/skills/sdlc/SKILL.md)
+- **Coding standards (priority ordering, PR discipline, tests, no-hardcoded-values, CalVer):**
+  [`groombook/org/skills/coding-standards/SKILL.md`](https://git.farh.net/groombook/org/src/branch/main/skills/coding-standards/SKILL.md)
+- **Safety (no plaintext secrets, no direct `kubectl apply` to `groombook`, no self-merge, board approval for destructive actions):**
+  [`groombook/org/skills/safety/SKILL.md`](https://git.farh.net/groombook/org/src/branch/main/skills/safety/SKILL.md)
+
+For human contributors and humans reviewing agent work, see
+[`CONTRIBUTING.md`](./CONTRIBUTING.md) in this repo for the phase-by-phase PR
+flow and the `uat→main` merge-gate policy summary.
+
+## Non-negotiable operational rules
+
+These mirror the org skills; they are restated here so any agent landing in
+this repo sees them without a cross-repo fetch.
+
+- **All changes go through a PR.** Never push directly to `dev`, `uat`, or `main`.
+- **Branch strategy:** `feature/<name>` → `dev` → `uat` → `main`. Engineers
+  always target `dev` first.
+- **No self-merge contract.** The engineer who opened a PR clicks merge only
+  after the named reviewer (CI / QA / UAT / Security / CTO per phase)
+  approves. Issue-thread QA / UAT / security approvals do **not** clear the
+  Gitea `required_approvals` gate on `uat→main` — only a Gitea **Approve**
+  click from a member of the `approvals_whitelist_username` does. On this
+  repo that whitelist is `["gb_flea", "gb_dogfather"]` (engineer team).
+  Board-level accounts cannot give the Approve click by policy.
+- **Always include `cc @cpfarhood`** at the bottom of every PR body for
+  board visibility (not as a reviewer).
+- **Secrets in code are forbidden.** Use Bitnami Sealed Secrets; never commit
+  plaintext. See the `safety` skill.
+- **Production (`groombook` namespace) is Flux-managed.** Never
+  `kubectl apply` directly. Infrastructure changes go through PRs in
+  `groombook/infra`.
+
+## Local development
+
+See the repo's own README, package scripts, and CI workflow. The
+authoritative pipeline (Gitea Actions, image build, deploy hooks) is the
+shared `groombook/infra` overlay; do not reimplement it here.
+
+## When uncertain
+
+If a task conflicts with the org skills, **the org skills win**. Open an
+issue in `groombook/org` to propose a change rather than encoding a local
+exception.

CONTRIBUTING.md

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+# Contributing to `groombook/api`
+
+Thanks for contributing. This document is the human-facing companion to
+[`AGENTS.md`](./AGENTS.md) and the authoritative
+[`groombook/org`](https://git.farh.net/groombook/org) skills. The org skills
+govern; this file is a quick-reference for the human/agent PR flow in this
+repo.
+
+## Branch strategy
+
+Three long-lived branches; one PR per promotion step.
+
+| Branch  | Environment | Who merges | Prerequisites for merge |
+|---------|-------------|-----------|-------------------------|
+| `dev`   | Dev         | Engineer  | CI passes               |
+| `uat`   | UAT         | Engineer  | QA code review approval |
+| `main`  | Production  | Engineer  | UAT validation + CTO Gitea Approve when the `uat→main` merge-gate policy applies (see below) |
+
+Engineers always target `dev` first. Feature branches: `<agent-name>/<short-description>`.
+
+## Phase-by-phase PR flow
+
+### Phase 1 — Dev
+
+1. Branch from `dev`: `git checkout -b <name>/<short-description> origin/dev`.
+2. Write code + tests. Run unit tests, type check, and lint locally (or rely on CI).
+3. Open a PR against `dev`:
+   ```bash
+   tea pr create --base dev --title "..." --body "..."
+   ```
+   Include `cc @cpfarhood` at the bottom of the body for board visibility.
+4. CI must pass. CI green → engineer self-merges.
+5. CI builds and deploys to Dev automatically.
+
+### Phase 2 — UAT promotion
+
+1. Open a PR from `dev` to `uat`.
+2. CI must pass.
+3. **QA (Lint Roller)** reviews and approves on the Gitea PR.
+4. QA approved → engineer self-merges.
+5. CI builds and deploys to UAT automatically.
+
+### Phase 3 — UAT regression + Security review
+
+1. **UAT (Shedward Scissorhands)** runs full regression against UAT — every
+   feature, old and new, no exceptions.
+2. **Security (Barkley Trimsworth)** reviews the changes.
+3. Failures in either gate bounce back to Phase 1.
+
+### Phase 4 — Production promotion (`uat → main`)
+
+This is the gate the org PR
+[`groombook/org#13`](https://git.farh.net/groombook/org/pulls/13) defines.
+The full rule is in
+[`groombook/org/skills/sdlc/SKILL.md`](https://git.farh.net/groombook/org/src/branch/main/skills/sdlc/SKILL.md)
+and
+[`groombook/org/skills/coding-standards/SKILL.md`](https://git.farh.net/groombook/org/src/branch/main/skills/coding-standards/SKILL.md);
+the summary is below.
+
+**The CTO Gitea Approve click is NOT the default gate.** Once the four
+pre-gates (QA, UAT deploy, UAT regression, security) are green, the engineer
+self-merges.
+
+**A CTO Gitea Approve click IS required** only for PRs in one of three
+categories:
+
+1. **Novel auth / session paths** — login, OIDC, OOBE, session middleware,
+   token issuance, password reset, MFA, new auth provider integrations.
+   Routine auth-gated UI (button styling, error messages, form layout) is
+   **not** in this category.
+2. **Infra / prod-affecting merges** — deploys, infra manifests, secrets,
+   GitOps overlays, CI/CD, `main` branch protection, production
+   routing/ingress, prod state mutations. All Phase 5 infra overlay PRs in
+   `groombook/infra` require CTO Gitea Approve without exception.
+3. **Risk-flagged merges** — `risk:cto-approve` label, or explicit CTO/CEO
+   sign-off request in the PR or issue thread.
+
+The engineer opens the `uat→main` PR, classifies it against the three
+categories above, and adds `cc @cpfarhood`. If the PR is in scope, the CTO
+clicks Approve; once approved (and the four pre-gates are green), the
+engineer merges.
+
+### Phase 5 — Production deployment
+
+A separate PR in `groombook/infra` bumps the overlay image tag for prod.
+Handed to QA (Lint Roller) for review, then self-merged by the engineer.
+
+## The four pre-gates (uat→main)
+
+A `uat→main` PR is mergeable when **all four** are green:
+
+1. **QA code review** — done on the dev→uat promotion PR.
+2. **UAT deploy** — the UAT image built from the uat tip is live in UAT.
+3. **UAT regression** — Shedward's full-feature UAT pass is green (no
+   pre-existing defects, no new defects).
+4. **Security review** — Barkley's security code review is green.
+
+Issue-thread QA / UAT / security approvals do **not** clear the Gitea
+`required_approvals` gate. Only a Gitea **Approve** click from a member of
+the `approvals_whitelist_username` for `main` clears it. In this repo that
+whitelist is the engineer team (`gb_flea`, `gb_dogfather`).
+
+## Style, tests, and quality bar
+
+See
+[`groombook/org/skills/coding-standards/SKILL.md`](https://git.farh.net/groombook/org/src/branch/main/skills/coding-standards/SKILL.md)
+for the engineering priority ordering, test requirements, no-hardcoded-values
+rules, CalVer versioning policy, and the `git.farh.net` container registry
+policy.
+
+## Safety
+
+See
+[`groombook/org/skills/safety/SKILL.md`](https://git.farh.net/groombook/org/src/branch/main/skills/safety/SKILL.md)
+for the non-negotiable rules: no plaintext secrets, no `kubectl apply` to
+`groombook`, no self-merge, no direct `tofu` runs, board approval for
+destructive actions, escalation protocol.