Phase 0: project foundations

[aaylward]

What

Implements Phase 0 of docs/PLAN.md: the foundations every later phase builds on.

• Bazel 9 workspace (bzlmod-only): MODULE.bazel (+ committed lockfile) with rules_cc and googletest; .bazelrc sets the C++20 baseline per platform, asan/ubsan configs, and the Bazel 9 --incompatible_autoload_externally shim for third-party BUILD files that predate the native C++ rule removal (our own BUILD files load() from @rules_cc explicitly). .bazelversion tracks 9.x.
• Hello-world runtime target: //runtime:core (smithy::Version()) with a GoogleTest test, establishing the runtime/include/smithy/<module> header layout from PLAN §3.1.
• Codegen Gradle skeleton (codegen/): smithy-cpp-codegen module against smithy-codegen-core/smithy-build 1.53.0, reserving the cpp-codegen plugin name with ServiceLoader registration, unit tests (JUnit 5), and Spotless/google-java-format.
• CI (GitHub Actions): Bazel build+test matrix (Linux gcc + clang, macOS, Windows MSVC), an ASan+UBSan job, a Gradle job (build spotlessCheck), and a lint job (clang-format, clang-tidy, buildifier).
• ADRs 0001–0004: JVM DirectedCodegen generator; restJson1 + rpcv2Cbor from the start; Outcome-based error handling with the C++20 compiler floor; Bazel 9 as the only supported build system.
• Fixture model corpus: examples/weather (restJson1: resources, HTTP bindings, pagination, modeled 404) and examples/cafe (rpcv2Cbor: enums, unions, idempotency token, client/server errors) — the models that drive tests in Phases 2–5.
• Repo hygiene: Apache-2.0 license, CONTRIBUTING.md, docs/development.md, .clang-format/.clang-tidy/.editorconfig/.gitignore, issue + PR templates, README status table.

Testing

Validated locally with the same commands CI runs:

• bazel test //... --config=ci — passes (Bazel 9.1.1, Linux)
• bazel test //... --config=ci --config=asan --config=ubsan — passes
• (cd codegen && gradle build spotlessCheck) — passes (JDK 21 targeting release 17, Gradle 8.14.3)
• clang-format --dry-run --Werror, clang-tidy, and buildifier --mode=check -r . — clean

The macOS/Windows legs of the matrix run for the first time in this PR's CI.

Checklist

• Tests added/updated for the change
• bazel test //... and (cd codegen && gradle build spotlessCheck) pass locally
• Formatting clean (clang-format, buildifier, spotless)
• Architectural decisions recorded as an ADR (ADRs 0001–0004)

🤖 Generated with Claude Code

https://claude.ai/code/session_01WjaNFwBZxoHdqagvq8ycQf

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Generated by Claude Code