feat: support local development using Buck2

.github/workflows/buck2.yml

@@ -0,0 +1,56 @@
+name: Buck2 (Experimental, non-blocking for PRs)
+
+on:
+  pull_request: {}
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+concurrency:
+  group: buck2-${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
+permissions:
+  contents: read
+
+jobs:
+  buck2-test:
+    name: buck2 test //codex-rs/...
+    runs-on: ubuntu-24.04
+    # Non-blocking while Buck2 support is still experimental.
+    # continue-on-error: true
+    timeout-minutes: 30
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      # scripts/buck2, scripts/reindeer, etc. are DotSlash wrappers.
+      - name: Install DotSlash
+        uses: facebook/install-dotslash@v2
+
+      - name: Setup Rust toolchain
+        uses: dtolnay/rust-toolchain@1.90
+        with:
+          # Match codex-rs/rust-toolchain.toml (and include rust-src for Buck2 toolchains).
+          components: rustfmt, clippy, rust-src
+
+      - name: Install system deps (Linux)
+        shell: bash
+        run: |
+          set -euxo pipefail
+          sudo apt-get update
+          sudo apt-get install -y pkg-config libssl-dev
+
+      - name: Setup Buck2 (local)
+        shell: bash
+        run: |
+          set -euxo pipefail
+          ./scripts/setup_buck2_local.sh
+
+      - name: Run Buck2 tests
+        shell: bash
+        run: |
+          set -euxo pipefail
+          ./scripts/buck2 test -c test.rule_timeout_ms=1800000 --test-executor-stdout=- --test-executor-stderr=- //codex-rs/...