clippy: added decision record on how to integrate clippy

docs/design_decisions/DR-006-infra.md

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+
+# DR-006-Infra: Clippy Integration via rules_lint
+
+- **Date:** 2026-01-19
+
+```{dec_rec} Clippy Integration via rules_lint
+:id: dec_rec__infra__clippy_rules_lint
+:status: accepted
+:context: Infrastructure
+:decision: Use rules_lint for Clippy in S-CORE modules
+```
+
+---
+
+## 1. Context / Problem
+
+S-CORE needs a consistent, Bazel-native way to run Rust Clippy across modules. We
+initially aligned on rules_rust for Clippy integration, but rules_lint added native
+Clippy support while that work was ongoing. We must choose one approach to reduce
+divergence and keep lint workflows maintainable.
+
+Key constraints:
+- Avoid running Clippy across the entire tree by default.
+- Avoid maintaining long, manual target lists.
+- Keep lint rules centralized and versioned.
+- Allow CI-friendly lint runs without additional tooling requirements.
+
+## 2. Decision
+
+We adopt rules_lint for Clippy integration in S-CORE modules.
+
+## 3. Rationale
+
+rules_lint fits better with the linting workflow:
+- It is designed for linting (output groups, lint tests, lint-oriented UX).
+- It avoids whole-tree runs and manual target lists by linting only the build graph
+  of requested targets.
+- Clippy support is released and tested, which reduces risk.
+
+rules_rust remains a valid option, but it requires manual target enumeration for
+lint-only runs and is harder to scope for incremental linting.
+
+## 4. Integration Approach
+
+Each module integrates Clippy through a rules_lint aspect:
+- Use the shared aspect from `@score_rust_policies//clippy:linters.bzl`
+  (repo-local aspects remain an option if needed).
+- Reference the centralized Clippy configuration from the policies repo:
+  `@score_rust_policies//clippy/strict:clippy.toml`.
+- Enable the aspect in `.bazelrc` via `build --aspects=...%clippy` and request
+  output groups `rules_lint_human` (and optionally `rules_lint_machine`).
+- Skip linting for specific targets using the `no-lint` tag.
+- For CI, add `--@aspect_rules_lint//lint:fail_on_violation=true` to fail on findings.
+- Use `aspect_rules_lint` >= `2.0.0-rc0` to support `fail_on_violation` with Clippy.
+
+This keeps configuration and behavior consistent while allowing each module to scope
+linting to the targets it builds.
+
+## 5. Consequences
+
+- Clippy runs on the Rust targets in the build graph of the requested Bazel targets,
+  not the whole repository by default.
+- Lint rules are centralized in `score_rust_policies`, reducing duplication and drift.
+- The Aspect CLI is not required for Clippy execution; standard `bazel build` works.
+- rules_lint uses Aspect telemetry; this can be disabled via repo environment
+  variables if required by policy.
+
+## 6. Future Considerations
+
+We may integrate the Aspect CLI in the future to enable the `bazel lint` command and
+additional lint UX (interactive output, filtering, reporting). This is optional and
+separate from the Bazel-based execution path.