create an AGENTS.md file

AGENTS.md

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+# AGENTS.md
+
+Guidance for coding agents working in **macOS-setup-scripts**.
+
+## Repository summary
+
+- Bash automation for provisioning a development-focused macOS environment (Homebrew, dotfiles, `defaults write`, and related setup).
+- Orchestrator: `src/scripts/master.sh`; shared helpers: `src/scripts/utils.sh`.
+- Dotfiles live in the `src/dotfiles/` git submodule (do not edit unless the task explicitly requires submodule changes).
+- User-facing docs: `README.md`.
+- CI on pull requests:
+  - **Quality Checks** (`.github/workflows/quality-checks.yaml`) — markdownlint, Prettier, ShellCheck, yamllint via [garretpatten/quality-checks](https://github.com/garretpatten/quality-checks).
+  - **Test Runner** (`.github/workflows/test-runner.yaml`) — runs scripts on `macos-latest` (skips heavy steps in `pre-install.sh`).
+
+## Layout
+
+```text
+src/scripts/          # Setup phases (*.sh); source utils.sh with shellcheck directives
+src/dotfiles/         # Submodule — separate repo; excluded from root Prettier runs
+src/assets/           # Static assets (e.g. wolf.txt)
+.github/workflows/    # GitHub Actions
+```
+
+## Shell script conventions
+
+- Use `#!/bin/bash` and `set` behavior consistent with neighboring scripts.
+- Source shared code with a ShellCheck hint, for example:
+
+  ```bash
+  # shellcheck source=utils.sh
+  source "${SCRIPT_DIR}/utils.sh"
+  ```
+
+- Prefer `utils.sh` helpers (`log_error`, `ensure_directory`, `copy_file_safe`, and so on) over duplicating logic.
+- Append recoverable command failures with `2>>"$ERROR_LOG_FILE" || true` where other scripts already do.
+- Keep changes scoped to the requested task; avoid unrelated refactors or drive-by formatting outside touched files.
+
+## Linter configuration
+
+| Tool              | Config                                      | Notes                                            |
+| ----------------- | ------------------------------------------- | ------------------------------------------------ |
+| markdownlint-cli2 | `.markdownlint.yaml`, `.markdownlintignore` | MD013 (line length) is off                       |
+| Prettier          | `.prettierrc`, `.prettierignore`            | `src/dotfiles/` is ignored at repo root          |
+| ShellCheck        | `.shellcheckrc`                             | `external-sources=true`, `source-path=SCRIPTDIR` |
+| yamllint          | `.yamllint`                                 | Line length max 80; `document-start` disabled    |
+
+## Required quality gate
+
+**Before you finalize any change** (end of task, commit, or PR), you **must** run all four linters below on every file you added or modified (and on any new files you created). Do not skip this step.
+
+1. Fix reported issues (use auto-fix flags where noted).
+2. Re-run checks until all four pass.
+3. In your final message, state that the four linters passed or list anything you could not run and why.
+
+If a tool is missing locally, install it (see [Prerequisites](#prerequisites)) or use the `npx` / `pip3` invocations below. Do not mark work complete while known lint failures remain in changed paths.
+
+## Prerequisites
+
+From the repository root:
+
+```bash
+npm ci
+```
+
+Install CLI tools if needed (macOS examples):
+
+```bash
+brew install shellcheck
+pip3 install yamllint
+npm install -g markdownlint-cli2   # optional; npx works without global install
+```
+
+Prettier is provided by this repo’s `package.json` after `npm ci`.
+
+## Running linters
+
+Run commands from the **repository root** so config files are discovered.
+
+### Changed files only (typical)
+
+Set a diff base (adjust branch name if needed):
+
+```bash
+BASE_REF="${BASE_REF:-origin/master}"
+git fetch origin master 2>/dev/null || true
+```
+
+Collect paths you changed:
+
+```bash
+mapfile -t MD_FILES < <(git diff --name-only --diff-filter=ACMR "${BASE_REF}"...HEAD | grep -E '\.(md|markdown)$' || true)
+mapfile -t SH_FILES < <(git diff --name-only --diff-filter=ACMR "${BASE_REF}"...HEAD | grep -E '\.(sh|bash|zsh)$' || true)
+mapfile -t YAML_FILES < <(git diff --name-only --diff-filter=ACMR "${BASE_REF}"...HEAD | grep -E '\.(yml|yaml)$' || true)
+mapfile -t PRETTIER_FILES < <(git diff --name-only --diff-filter=ACMR "${BASE_REF}"...HEAD | grep -E '\.(js|jsx|ts|tsx|json|css|scss|md|yml|yaml)$' || true)
+```
+
+Then run (skip a tool when its file list is empty):
+
+```bash
+# markdownlint — check
+[[ ${#MD_FILES[@]} -gt 0 ]] && markdownlint-cli2 "${MD_FILES[@]}"
+
+# markdownlint — fix, then re-check
+[[ ${#MD_FILES[@]} -gt 0 ]] && markdownlint-cli2 --fix "${MD_FILES[@]}"
+
+# Prettier — check (matches CI)
+[[ ${#PRETTIER_FILES[@]} -gt 0 ]] && npx prettier --no-error-on-unmatched-pattern --check "${PRETTIER_FILES[@]}"
+
+# Prettier — write, then re-check
+[[ ${#PRETTIER_FILES[@]} -gt 0 ]] && npx prettier --no-error-on-unmatched-pattern --write "${PRETTIER_FILES[@]}"
+
+# ShellCheck
+[[ ${#SH_FILES[@]} -gt 0 ]] && shellcheck "${SH_FILES[@]}"
+
+# yamllint
+[[ ${#YAML_FILES[@]} -gt 0 ]] && yamllint "${YAML_FILES[@]}"
+```
+
+Without a global `markdownlint-cli2`:
+
+```bash
+npx --yes markdownlint-cli2 "${MD_FILES[@]}"
+npx --yes markdownlint-cli2 --fix "${MD_FILES[@]}"
+```
+
+### Full-repo checks (when unsure what changed)
+
+Use when you touched many paths or want parity with a broad local sweep:
+
+```bash
+npx --yes markdownlint-cli2 "**/*.md"
+npx prettier --no-error-on-unmatched-pattern --check .
+shellcheck src/scripts/*.sh
+yamllint .github .yamllint .markdownlint.yaml
+```
+
+Prettier honors `.prettierignore` (including `src/dotfiles/`). Yamllint loads `.yamllint` from the current directory.
+
+## Typical validation order
+
+1. **Shell** (`.sh` under `src/scripts/`): `shellcheck`
+2. **YAML** (`.github/`, root `*.yaml` / `*.yml`): `yamllint`
+3. **Markdown**: `markdownlint-cli2` (fix with `--fix` if needed)
+4. **Prettier** (JSON, Markdown, YAML, and other supported types in scope): `prettier --check` after any `--write`
+
+## Before finishing (checklist)
+
+- [ ] `markdownlint-cli2` passed on all changed Markdown files
+- [ ] `npx prettier --check` passed on all changed files Prettier handles (respecting `.prettierignore`)
+- [ ] `shellcheck` passed on all changed shell scripts
+- [ ] `yamllint` passed on all changed YAML files
+- [ ] No unrelated files were reformatted or lint-fixed outside the task scope
+- [ ] If a linter could not be run, that fact is called out explicitly in the summary
+
+## Commits and pull requests
+
+- Create commits only when the user asks.
+- Pull requests are validated by **Quality Checks** and **Test Runner**; local runs above should match CI behavior for the four linters.
+- Do not modify `src/dotfiles/` unless the task requires it; submodule changes have their own workflow in that repository.