docs: add Agent Guide with source of truth, architecture, testing, and PR guidelines

Author: zliang-akamai

AGENTS.md

@@ -0,0 +1,71 @@
+# Agent Guide
+
+## Source of Truth
+
+- This is the official synchronous Python SDK for the Linode API. Supported
+  Python versions come from [pyproject.toml](pyproject.toml) (`>=3.10`); do not
+  infer support from the older environment names still present in [tox.ini](tox.ini).
+- Make changes only in canonical source trees such as `linode_api4/`, `test/`,
+  `docs/`, `examples/`, and `.github/`. Do not edit generated copies or output in
+  `build/`, `dist/`, `docs/build/`, `docs/_build/`, or `linode_api4.egg-info/`.
+- `linode_api4/version.py` is generated by `make create-version` and `make build`.
+  Do not hand-edit it for ordinary feature work.
+- Use [README.rst](README.rst) for setup and test details and
+  [CONTRIBUTING.md](CONTRIBUTING.md) for contribution policy. Keep this file
+  limited to guidance that is easy to miss while navigating the repository.
+
+## Architecture and Implementation
+
+- `linode_api4/linode_client.py` owns HTTP behavior and wires API groups onto
+  `LinodeClient`; `linode_api4/groups/` exposes operations; `linode_api4/objects/`
+  defines resource models; `linode_api4/paginated_list.py` handles collection
+  pagination.
+- Follow the nearest existing group method, model, and unit test before adding a
+  new pattern. Collection methods normally use `client._get_and_filter(...)`;
+  create/update/delete methods use the client's request helpers and return model
+  objects where appropriate.
+- Models are lazy-loaded, and reading an unknown or stale property may issue an
+  API request. Read [docs/guides/core_concepts.rst](docs/guides/core_concepts.rst)
+  before changing model properties, relationships, filtering, or pagination.
+- New public models must be exported from `linode_api4/objects/__init__.py`. New
+  groups must be exported from `linode_api4/groups/__init__.py` and wired into
+  `LinodeClient`. Preserve public API compatibility unless the task explicitly
+  requires a breaking change.
+- Public behavior belongs in Sphinx-compatible docstrings and, when needed, the
+  source files under `docs/`. Never edit rendered documentation.
+
+## Tests
+
+- Start with the narrowest relevant unit test, for example
+  `python -m pytest test/unit/objects/linode_test.py -k test_name`. Run
+  `make test-unit` for the full mocked unit suite.
+- Unit tests normally extend `test.unit.base.ClientBaseCase`. GET requests are
+  resolved from JSON under `test/fixtures/`; use `mock_post`, `mock_put`, and
+  `mock_delete` for other verbs and assert the captured URL, body, or headers.
+- Fixture names encode endpoint paths: a single underscore becomes `/`, while a
+  doubled underscore becomes a literal `_`. Paginated fixtures containing
+  `results` also provide per-ID responses automatically when items include an
+  `id` field. See
+  `test/unit/fixtures.py` before inventing custom request mocking.
+- `make test-int` and `make test-smoke` call the live Linode API, require
+  `LINODE_TOKEN`, and may create or delete real resources. Run them only when the
+  change requires live validation and the environment is intentionally configured.
+
+## Formatting and Validation
+
+- Install development dependencies with `make dev-install`.
+- Formatting is Black + isort + autoflake with settings in [pyproject.toml](pyproject.toml).
+  `make format` rewrites all of `linode_api4/` and `test/`, so review the worktree
+  before and after using it for a focused change.
+- `make lint` is the broad CI-equivalent check: it builds distributions, checks
+  formatting/imports, runs pylint, and validates package metadata. Prefer focused
+  tests first because this target regenerates build artifacts and version metadata.
+
+## Pull Requests
+
+- Target the `dev` branch unless the task specifies otherwise.
+- PR titles must use `TPT-1234: Description`; CI exempts only the labels documented
+  in [.github/workflows/ci.yml](.github/workflows/ci.yml).
+- Keep changes focused, add tests for behavior changes, and use
+  [.github/pull_request_template.md](.github/pull_request_template.md) when drafting
+  the PR description.