Add review instructions for build infra and root config

.github/copilot-instructions.md

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+# Review rules for all PRs
+
+## 0. What not to flag
+
+CI already runs deterministic gates on every PR. If a gate would catch it, the gate reports it, 
+and a duplicate review comment is noise:
+
+| Gate | Covers |
+| --- | --- |
+| `precommit` (ruff, ruff-format, uv-lock, rstcheck) | Lint rules, formatting, import order, line length, `uv.lock` freshness, RST syntax |
+| `typecheck` (pyright, strict) | Type errors and unused `type: ignore` in packages listed under `[tool.pyright] include` |
+| `spellcheck` (codespell) | Spelling in code, docs, and comments |
+| `shellcheck` | Shell script correctness in `scripts/*.sh` |
+| `readme` | `README.rst` renders on PyPI |
+| `docs` | Docs build |
+| `generate` | The generated instrumentation README table being up to date |
+| `lint-license-header-check` | Missing license headers |
+| `oldest-deps-check` | Redundant pins in `tests/requirements.oldest.txt`, packages missing an `oldest` requirements file |
+| `changelog` workflow | Direct edits to `CHANGELOG.md`, changelog fragment presence |
+| `test` matrix | Test failures across the `oldest`/`latest`/`conformance` envs |
+
+Review the things a gate cannot decide: whether the change is correct, whether it matches the
+GenAI semantic conventions, whether it actually achieves what the PR claims, and whether it
+weakens or bypasses a gate. Style opinions that ruff does not enforce are not review comments.
+
+## 1. Shared configuration
+
+Repo-wide config is `tox.ini`, `pytest.ini`, root `pyproject.toml`, `.codespellrc`,
+`.pre-commit-config.yaml`, and `scripts/`. A change there affects every package, so:
+
+- **No developer-local paths.** Personal venv or scratch directory names must not be added to
+  shared configs. `.gitignore` already covers `venv*/`, `.venv*/`, and `.tox`; anything else
+  belongs in a local ignore or gets renamed to match those patterns. Flag entries that only make
+  sense on one contributor's machine.
+- **Skip lists must not weaken a gate.** Excluding a bare directory name from a lint or license
+  check also excludes any real source directory that happens to share that name. Prefer
+  path-anchored patterns (`*/.tox/*`) over bare components (`.tox`).
+- **Shell must be portable.** Commands in `tox.ini` and `scripts/*.sh` run on both Linux and
+  macOS. Flag GNU-only flags (e.g. `xargs --no-run-if-empty`, `sed -i` without a backup suffix,
+  `readlink -f`).
+
+## 2. Config that packages can shadow
+
+Root config does not automatically reach every package. Before approving a change to a root
+setting, check whether packages override the same section in their own `pyproject.toml`:
+
+- `pytest.ini` is only read when pytest's config lookup does not stop at a package
+  `pyproject.toml` first. These packages define `[tool.pytest.ini_options]` and therefore ignore
+  root `pytest.ini` entirely: `anthropic`, `agno`, `crewai`, `smolagents`, `llama-index`,
+  `claude-agent-sdk`. A new root pytest setting must either be added to each of them, or those
+  blocks removed.
+- The same applies to `[tool.ruff]` and `[tool.pyright]` overrides.
+
+Flag a root-config change whose stated goal ("fixes the warning everywhere", "applies to all
+tests") is not actually achieved for the shadowing packages.

.github/instructions/build-config.instructions.md

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+---
+applyTo: "tox.ini,pytest.ini,pyproject.toml,uv.lock,.codespellrc,.pre-commit-config.yaml,scripts/**,.github/workflows/**,.github/actions/**"
+---
+
+Review rules for PRs touching build, test-matrix, and CI configuration. Flag violations with a
+link to the rule. See [copilot-instructions.md](../copilot-instructions.md) for the repo-wide
+rules on shared config, portability, and shadowed settings, and for the gates whose findings must
+not be repeated as review comments.
+
+These rules cover what CI cannot check: a test env that is never run, a bound that is never
+exercised, a gate that silently stops covering ground. All of them pass CI while being wrong.
+
+## 1. Test matrix completeness
+
+A new package under `instrumentation/<pkg>/` must be wired into `tox.ini` in full. Check each of
+these, not just the first:
+
+- `envlist`: `py3{…}-test-instrumentation-genai-<lib>-{oldest,latest}`, the matching
+  `-conformance` entry, and `lint-instrumentation-genai-<lib>`.
+- `[testenv] deps`: the factor-conditional `-r …/tests/requirements.<factor>.txt` lines plus
+  `{[testenv]test_deps}` / `{[testenv]pytest_deps}`. Requirements install here, **not** in
+  `commands_pre`.
+- `[testenv] commands`: the pytest line (which must `--ignore` `tests/test_conformance.py`), the
+  separate `-conformance` pytest line, and the `lint-…` ruff line.
+- `[testenv:typecheck] deps`: `{toxinidir}/instrumentation/<pkg>[instruments]`.
+
+The uv workspace picks up new packages via the `instrumentation/*` glob in root `pyproject.toml`,
+so no edit is needed there.
+
+## 2. Lower bounds
+
+The `oldest` factor sets `UV_RESOLUTION=lowest-direct`, so lower bounds come from
+`pyproject.toml` and `oldest-deps-check` already enforces that invariant. Do not re-report what
+it catches.
+
+What is left to review is whether a changed bound is justified: a raised floor needs a reason in
+the PR description (a feature or fix the code now depends on), and a lowered floor needs evidence
+that the older version actually works, not just that the env resolves.
+
+## 3. Pyright scope
+
+`[tool.pyright] include` is opt-in and grows one package at a time. Typing more code is the goal,
+so review changes here by direction:
+
+- Adding a package to `include` is welcome. `src/**` is never excluded.
+- Excluding a package's `tests/**` and `examples/**` is the current convention when it joins
+  `include`, but only as a stopgap (see the comment above `exclude`). A PR that types its tests
+  and drops the exclusion is an improvement.
+- Flag the reverse: a package removed from `include`, or a `src/**` path added to `exclude`, to
+  make a type error go away.
+
+## 4. Lint and check scripts
+
+A change that narrows what a check scans (new skip entry, new exclude path, a `|| true`) must say
+why in the PR description. Silent scope reduction on a gate reads as "still passing" when it no
+longer checks the same ground.
+
+See also [AGENTS.md](../../AGENTS.md) for general repo rules.